I think the reliability of Wikipedia varies a lot by topic, but if all you want is a "casual overview" of something then I usually find it pretty good. Most of the articles on pirates are "tolerable I suppose" with some minor errors, although I sometimes come across more glaring inaccuracies every now and then. Just don't completely trust anything you read there until at least checking the sources.

I actually remember what first inspired me to start really researching pirates and buccaneers was reading a Wiki article about Henry Morgan and his sack of Panama in 1671, in which he led an army of 2,000 buccaneers across the Isthmus where they then fought and defeated the Spanish in a battle. That immediately struck me as so strange and fascinating and almost fake sounding, and I immediately felt I had to know more about it. I believe I then checked the sources and read three great books about the topic. These were The Sack of Panama: Captain Morgan and the Battle for the Caribbean by Peter Earle, Empire of Blue Water by Stephen Talty, and The Buccaneers of America published in 1678 by a French buccaneer named Alexandre Exquemelin who was actually present at the sack of Panama. Another current great interest of mine, the shipwreck and mutiny of the Dutch East India ship Batavia in 1629, was inspired by my first finding the Wiki article about it while randomly looking through a Wikipedia list of Australian shipwrecks. I then followed the listed sources to find Mike Dash's wonderful book Batavia's Graveyard: The True Story of the Mad Heretic Who Led History's Bloodiest Mutiny and later a translation of the original journals.

I think the main point on this subreddit of not using Wikipedia as a source for answers is that often there are many small errors in Wiki articles and sometimes much larger errors and ommissions, and the answers here are supposed to be from people who have actually done enough of their own research on a topic that they can say with real certainty and authority that it's reliable, something you can never get by solely relying on Wikipedia for any claim. But for just a quick overview of a topic out of personal interest and with a desire to check sources and learn more from actual written sources? In my opinion it's generally pretty alright for that.

With history, unfortunately, (Or fortunately, depending on your outlook) there just isn't any replacing books. For my discipline, at least, the popular wisdom is often really out of line with the historical consensus, so that's made me pretty skeptical of Wikipedia. The thing that might be closest to what you're looking for is the Very Short Introduction series Oxford publishes. It's not at all limited to history, there are hundreds of them out there, they're quick, readable, written by serious scholars in their field, and, importantly, very cheap. (I've found them for $7-10 pretty easily, and you probably could find them for less if you dug around for deals)

You also generally can't go wrong with the Oxford and Cambridge companion series, or other similar books. (These are the most widespread, but I think other universities also publish these sort of things) They're a little pricier ($15-20 usually) and more scholarly, but are still generally pretty easy for a novice to pick up and read. The AskHistorians Booklist will also frequently have intro books in specific subjects.

For my field, literature, the Norton Anthologies are pretty standard undergrad reading, they're generally composed of a lot of primary sources, so they may not necessarily be easy, but they're usually fairly well glossed and have useful reference materials. Norton's critical editions of famous works are also not bad, though at least for Shakespeare I usually prefer the Signet Classics editions, but this is all getting pretty far afield. Hope that was helpful, and keep in mind you can always come and ask here if you want book recommendations.

Unironically, coming to this sub and searching for an answer is usually a good start.

This depends a lot on what you mean by causal and what you found useful about Wikipedia. I know that I liked how there was so much knowledge in one place and pretty much everything had an article. I do not think you are going to find an easy replacement for that. Similarly, I found that Wikipedia articles were often pretty easy to read (although I have not checked their lexile level), while other sources might be harder. My thought is that the main things that might help will be subject/field specific encyclopedias, reviews and podcasts, and some side publications as it were. I've ordered the categories roughly in how useful I think they'll be.

#Summary I think the encyclopedias I mentioned will have the most info for you, but might not be casual enough. Since your issue with EB is that it is too sketch like, I'm putting them first though. The podcasts I think are really casual (I listen to them while exercising, in transit, and cooking) but depending on your tastes might not provide enough information or assume too much pre-existing knowledge. The reviews have a similar problem. The side publications might scratch that itch but might be a bit too focused on the profession. The miscellanea is there if you want to dig deeper.

#Encyclopedias An issue here will be that since they are not general encyclopedias, they might have gaps that you would want filled. But within their field they will probably be better than Encyclopedia Britannica. Most of the ones I know are for European History due to my own interests.

For online ones, I'd suggest European History Online, The International Encyclopedia of the First World War, and the United States Memorial Holocaust Museums' Holocaust Encyclopedia.

The first (EGO for its German name) comes with both English and German articles. I have somewhat mixed feelings about it, in that I think it's organized in a rather intuitive way (e.g. I'm pretty sure there is no article about, say, Germany but there is an article about "The West" as a category), but I think it can be a really interesting place to read about concepts and categories used in European History. The second is breathtakingly detailed, having an article dedicated to Ottoman Food Policy (and I think Food Policy for many of the countries involved), although as its name implies it only covers the First World War. It is a peer reviewed source (as was EGO) sponsored by the Free University of Berlin and the Bavarian State Library, which gives me hope it won't disappear anytime soon. I've actually practically used the third, to help understand what the Kielce Pogrom was, since I was reading references to it but none had any analysis. I will comment here that I find EGO the least fun/hardest to read.

For dead-tree encyclopedias, I've gotten a lot of use out of both the Encyclopedia of European Social History and the New Dictionary of the History of Ideas. The former deals primarily with social history (so, roughly, demography, working-class history, economic history, etc. and less on either the military side or political side), while the former is set up as a dictionary and has nice review essays on different key concepts. As someone trying to branch out into more Political Science, I found the article on Game Theory pretty helpful.

These are the five that I know, but there are certainly more. If you look around, you'll find some.

#Book Reviews and Podcasts

These might vary, since I've found some book reviews do a good job of summarizing and analyzing the book while putting the work into broader context (which, I think, if you want to learn history will help you), but others focus primarily on critiquing it (which might be helpful to you, but might require more background knowledge on your part). With that said:

H-Net, despite having a new and terrible interface, still publishes good reviews. You can find a list of all review (going back to 1994!) published on H-Net here. You can also use more advanced tools (key word searches, limiting to specific networks [read: subject fields], etc.) to search the reviews. Similarly, but having a much nicer interface, is the Institute for Historical Research's Reviews in History. These might help you get a sense of the arguments historians make and what books to buy/pirate.

If you like things more audio than written, Cambridge has a new podcast out called Interventions which deals with intellectual history. Being not an intellectual historian, I cannot vouch for its quality. Similarly, The History of Philosophy without any Gaps is a pretty good primer on history of philosophy with the entire thing being slowly transformed into a series of books. Finally, and my personal favorite, Ottoman History Podcast has wonderful episodes that can range from discussion on the history of science to aroma in the Ottoman world. The hosts and guests are almost all either PhD candidates or working historians.

#Side Publications Here I mean those publications published by academic organizations but which are not themselves academic journals. These might be less interesting since they are more about the profession than about history per se but sometimes they might help scratch that itch. History Workshop is an academic journal, but also publishes free articles mostly on Marxian/Left-leaning British History. Another example would be Perspectives published by the American Historical Association (although in my experience that tends to be more teaching and meta commentary on the historical profession). Similarly, the Organization of American Historians publishes Process which has a mix of professional commentary on being a historian and articles analyzing events (e.g. their recent series of sports and drug use).

#Miscellanea You also might want to try some of those big introductory books. Despite strong political differences, I really enjoyed Tony Judt's Postwar, which is a history of Western and Eastern Europe after World War II. It's a big book, but you can read it slowly (that's what I did). Try intro college textbooks (your Western Civ, your World History, your American History, etc.). Those can be annoyingly dry, but can give you a lot of detail if that's what you're after.

You might also want to check out companion books. I'm going to try to finish either the Blackwell Companion to Europe between 1900-1945 or the Blackwell Companion to Europe since 1945 by the end of the summer. I think those though might be a little outside of casual though. (Honestly while I like anthologies, I do find the switch to different narrative voices and the lack of a continuous development of ideas rather um annoying and often just use them to scour citations for other works.)