Eh, I would say yes and no, for a couple of reasons.

First, it definitely isn't just miltech, though you are absolutely correct it is heavily that. I would say there is also, for example, "light side" and "dark side" machining/mechanical content. Abom79 and Blondihacks are pure "light side". Zip Ties and Bias Plies was "dark side," though as a fellow Borderer-descended redneck asshole, I am sure that as with many former "Canadian American Patriots," he has smartened up pretty damn fast in recent months. AvE started out light side, lost his way for a while, and lately is with genuinely admirable sheepishness comporting himself so as to suggest embarrassed recognition of his prior excesses. And there are lots I just "don't recommend channel"/"not interested" as soon as I see it. I also see the same for gaming - I like some classic Doom mods that some fascist infants also have strongly stupid opinions about, for example - and from this I conclude that there is something in essentially any genre that might support it. I doubt I would observe the same in makeup tutorials, for example, but the days when eyeliner improved my looks lie decades behind me now.

Second, miltech and history content on YT does not remotely for the most part constitute "reasonable documentaries," unless you refer to forgotten VHS and DVD transfers that are never surfaced anywhere unless you search for them by name. Not to indict modern "creators" (screenwriters, actors, directors, artists etc) en masse, of course. But few today even strive for the standard that older stuff, made before mere record-high count of eyeballs was taken as the only end, reached as a matter of course.