Haven't watched the video, but both of those comparisons seem wrongheaded to me. BG3 is coming out more than two decades after Throne of Bhaal. Both ME3 and Witcher 3 came out just a few years after the previous games. Further, at least with ME3 (I haven't played any Witcher games), there was a steady progression away from the RPG-like structure of ME1 as the games progressed, an effort to make the games more "approachable" etc. But, at least in my experience, what that mostly did was flatten the game experience into being little more than a waist-high-wall shooter with some flashy bits. ME1 actually felt like you had to learn some things. By the time it got to ME3, it felt like all you had to "learn" was twitch reflexes.
BG3, on the other hand, is trying very hard to keep as much of the spirit of D&D 5e's rules as it can, only making concessions for quality of life stuff where there's a clear, tested benefit. Further, it spent a long time in Early Access, whereas (AFAIK) neither ME3 nor Witcher 3 spent any time in Early Access at all, and certainly didn't respond strongly to major customer feedback from that. I suspect, if they had, ME3 would not have had the extremely controversial ending it did. (I still remember the clip of some important figure for the ME franchise explicitly saying that Mass Effect would not end up being a "pick a color" type ending....only to end up being EXACTLY that, red/blue/green energy explosions.)
More or less, if BG3 is "an anomaly," it's only because people are trying to shoehorn it into a comparison that doesn't work in the first place. At least, that's my thesis without having watched the video.