Well, the argument of "Who started the First World War?" has been something debated in historical circles almost since the war itself. Dozens if not hundreds of books have been written on the subject and arguments have been picked over again and again and again. I think almost everyone has potentially received blame for starting the war, including the UK (per Niall Fergusson's The Pity of War), and I would go so far as to say there is no real historical consensus on who exactly is responsible. The accusation that Germany was responsible has solid ground to stand on, however.

The traditional argument for Germany's guilt is best summarized in the Fischer Thesis. In the 1960s, German historian Fritz Fischer spent significant time studying the government archives and came to the conclusion that Germany intentionally instigated WWI in order to assume supremacy in Europe. Fischer's thesis has variously been attacked and supported since then and there is compelling evidence on both sides of the argument. There is little doubt that at the time of WWI, Germany was desperately afraid that it would lose its status as a great power as its geopolitical rivals slowly suffocated it. Richard Hamilton and Holger Herwig note that, "There existed in German ruling circles a desperate belief that time was running against Germany and that war alone could rejuvenate the Reich." There is also little doubt that the idea of a "preventative" war was taking root in German military circles at the time, alongside a deep-rooted fear of complete encirclement by rivals should Austria-Hungary falter in its conviction or internal stability. The embodiment of this paranoia is the Schlieffen Plan, the ultimate offensive war model meant to initiate a conflict and relatively quickly end it to the benefit of Germany. HW Koch explains that, "“German military planning was dominated by this fear [of encirclement], as well as by Germany's geographic position, which allowed only a preventive defensive stroke. The Schlieffen plan was its ultimate expression." This fear of encirclement and destruction also necessitated continued and strong support to an increasing unstable and flagging Austria-Hungary. In short, it can't be said that Germany was eager to maintain peace on the eve of WWI. At the very least, even if they didn't start the war intentionally, through its blank cheque to Austria among other factors, the German government is guilty of removing its support for the balance of power system that was maintaining peace in Europe but not working to Germany's interests.

It should be noted that your referenced example of Germany offering a treaty with France should be treated with a certain amount of ridicule. Germany never intended to fight a war that didn't involve an invasion of France. The Schlieffen Plan's complete domination of all German military planning prior to the war clearly demonstrated that Germany was not just willing to leave France out of the conflict while it dealt with Russia. When German officers envisioned a war, as the HW Koch quote shows, they envisioned one following the Schlieffen Plan which necessitated an invasion of France (and, by extension, an invasion of neutral Belgium that would prompt British intervention). Germany knew exactly what they were doing when mobilization started. They were embarking on a war for hegemony in Europe, not a jaunt to smack around Russia.

In reference to the UK/France wanting to destroy Germany, I think you're overstating this. It can be convincingly said that the UK (and France to a certain extent) wanted to maintain the balance of power in Europe. Germany's rising power and aggressive overtones, like its sudden naval build-up to try and contest British naval superiority, alarmed the UK because it represented a potential source of instability. Peter Gellman points out that Sir Eyre Crowe, Permanent Undersecretary of the British Foreign Office, viewed the role of Britain in turn of the century Europe as the great guarantor of balance of power relations. Winston Churchill (biased though he may be), reaffirmed this view in The Gathering Storm when he points out that, "For four hundred years the foreign policy of England has been to oppose the strongest, most aggressive, most dominating Power on the Continent..." Britain was merely playing to its self-appointed role in the international system. Indeed, up until the naval arms race, Britain and Germany had had remarkably good relations with one another. France, and to a greater extent, Russia, were viewed as the traditional foes of Great Britain. France is hardly to blame for wanting to "destroy" Germany either. The beating it received at the hands of Prussia made it very clear to France that it needed to maintain its defenses and the European balance of power to prevent such a thing from ever happening again. When they went to war, they went because they had very little choice in the matter. They could let Germany just take their major fortress-city and they couldn't just stand by as the system that was guaranteeing their survival was on the brink of collapse. Also, they were attacked, so, you know, that helped. Joachim Remak rightly points out that, "The French, in 1914, entered the war because they had no alternative. The Germans had attacked them. History can be very simple at times."

So, is Germany guilty of starting two world wars? There's no doubt that they started WW2. None. But as far as WWI goes, with the amount of ink that's been spilled on the subject, I can't really make a long, compelling argument in a simple Reddit comment. Personally, I think that Austria and Germany equally share the guilt. The two powers, more than any other, lashed out at the balance of power system because it wasn't working for them and were undoubtedly the most willing to play fast and loose with peace and war because they both felt their destruction/slide from great power status was imminent if they didn't do something risky. As GF Hudson once noted, "There is perhaps no factor which drives a state to war so inexorably as a steady loss of relative power. Sooner or later, a desperate now-or-never mood overcomes the calculations of prudence, and the belief that a war may be won today, but cannot be won tomorrow, becomes the most convincing of all arguments for an appeal to the sword."

If you're interested in reading up on this more, I suggest James Joll's The Origins of the First World War as a good overview of numerous arguments for and against various causes.

Also, "winners write history" is a worn out trope that is best avoided. Winners don't write history. People do. I'll just leave you with r/history's bot write-up on the subject:

It seems like you are talking about the popular but ultimately flawed and false "winners write history" trope!

It is a very lazy and ultimately harmful way to introduce the concept of bias. There isn't really a perfectly pithy way to cover such a complex topic, but much better than winners writing history is writers writing history. This is more useful than it initially seems because until fairly recently the literate were a minority, and those with enough literary training to actually write historical narratives formed an even smaller and more distinct class within that. To give a few examples, Genghis Khan must surely go down as one of the great victors in all history, but he is generally viewed quite unfavorably in practically all sources, because his conquests tended to harm the literary classes. Or the senatorial elite can be argued to have "lost" the struggle at the end of the Republic that eventually produced Augustus, but the Roman literary classes were fairly ensconced within (or at least sympathetic towards) that order, and thus we often see the fall of the Republic presented negatively.

Of course, writers are a diverse set, and so this is far from a magical solution to solving the problems of bias. The painful truth is, each source simply needs to be evaluated on its own merits.

Sources

Koch, H. W. "Introduction." In The Origins of the First World War, edited by H. W. Koch, 20. 2nd ed. Basingstoke: Palgrave MacMillan, 1984.

Hamilton, Richard F., and Holger H. Herwig. Decisions for War, 1914-1917. Cambridge: Cambridge University Press, 2005.

Churchill, Winston. The Gathering Storm. Harmondsworth, England. Penguin Books, 1948.

Joll, James, and Gordon Martel. The Origins of the First World War. 3rd ed. Harlow, England: Pearson Longman, 2006.