I'm not sure what "History Channel" bad means now days, but I would say it's pretty bad and the other Japanese flairs as far as I know agree with me.

I am not going to go through a minute-by-minute, point-by-point correction of the documentary. The documentary really depends on the section and which expert is responsible for the narrative. Nagashino was the best segment as they basically let Nate Ledbetter take the segment, and he was a regular contributor to samurai podcast and samurai forum who focuses on the latest research for Nagashino. Most of the documentary, like Okehazama, ninja training, and Sekigahara uses traditional narratives that have been overturned, but perhaps are slower to transfer to popular knowledge. Some things, like Mochizuki Chiyome the female ninja and Date Masamune plugging his eyes out, exist basically only in fiction. Then there are some really BS claims like Hideyoshi going mad from syphilis or the death tolls from Mount Hiei given by Turnbull. A lot of the timeline is jumbled up. The map is particular bad. I'm not sure if there's a single map in the entire six episodes that is accurate.

The documentary also suffers from two important things:

One, it obviously had a short and incorrect narrative summary in mind before production. For every subject it cuts segments from its many expert interviews that fit its narrative, instead of letting one or two experts explain and build the documentary around that. While the latter method wouldn't necessarily be more accurate, the former means they have many experts saying basically the same thing, taking up lots of unnecessary time. Time which could've been used to give more background information, especially regards the socio-political and economic situation that would've further help make sense of the events. It's really not surprising Nagashino, when they basically let one expert take over, is the most well done. This is not helped by the fact that everyone talked so slowly and the amount of random segments of nudity or people getting killed that serve no purpose. This leads me to

Two, the sheer, over-the-top brutality of the Sengoku Jidai seem to be its only focus. The re-enactment section basically have everyone behave like blood-thirsty yakuza rather than samurai and daimyō. Obviously some things, like the building and location, couldn't be helped on what is obviously a bare-bone budget. But others could have been much better. Some things are cultural things that would've added to the authenticity (they had Hideyoshi sit on a chair as if a throne instead of cross-legged on a raised platform). But more importantly, the entire thing is portrayed as unnecessarily cruel and illogically barbaric instead of everyone trying their best, issuing new laws, reorganizing the political system, and otherwise attempting to build a stable society within the system and situation given. That left a fairly bad taste for me.

The documentary also makes some very questionable decisions. For instance it plays up the katana, with little to no mention of any polearms, when I would say most people interested in Japanese history would know the main close-quarter weapon would've been some type of polearm. It also had the actor for Toyotomi Hideyoshi kill Imagawa Yoshimoto, which make it seem like Hideyoshi killed Yoshimoto in person (he didn't of course). A lot of interesting and important episodes or groups and people, like the Jesuits or the actual war against Ikkō Ikki were completely left out. It for some reason showed the burning of Mount Hiei for fighting the Ikkō Ikki, when Enryakuji would've no doubt been very annoyed if someone associated them with the Ikkō. Half of Date Masamune's episode also seem meaningless as they exaggerated him to make him seem like a credible rival to Hideyoshi only to have him surrender without a fight anticlimatically. The time definately could've been used for other things.

Overall, I would prefer one of the many YouTube videos on the Sengoku, despite their inaccuracies, to this Netflix series. But at least they didn't go down the road of aliens.