As someone who could be called a hardcore DOS fan (though I've only played DOSII. On the other hand, I beat it about five times, plus went seven or eight times through early access and wrote a lot of the TV Tropes page for it (including quite a bit of the stuff about Sebille, more on BG I and II in a second), I am not at all disappointed, so I'm not sure if you've overstated your opinion by applying a too wide brush to opinions fans of DOS and BG or I'm just unique (and I doubt there's any way to know short of interviewing a random sample of about 1% of BG III buyers).*
On BG I and II, while I only cleared the first one once and the second one I only got about halfway through before getting bored (I'll explain why in a different thread), I can say that I see a lot of BG and D&D in this game already. Do things need to be changed up to make a better fit? Hell yeah! Does it play like DOS with a D&D skin on top or just using DOS solutions to all problems? Only if I focus on the most obvious (and in some cases, most superficial) details. Scratching the surface, I feel like it's very much a modernized BG with elements of Dragon Age in it (the origin story: basically going from a skilled nobody (in most origins) to part of something bigger without any choice in the matter, as the player character did in DA:O, though this time from the villainous side and fully animated and voiced character dialogue and cutscenes, both of which BG I and II and DOS II lacked). Also, I'm sure more ties into BG I and II will be made as we actually get closer to (and eventually into) Baldur's Gate.
* Really that's a problem I keep seeing here, people treating their own experiences and opinions as the baseline, most broadly accepted, applicable ones. It's why I always am careful to state I'm only speaking for myself, because I am. It's also why I challenge people who seem to make that mistake.
), but no, its definitely not only superficial what makes BG3 closer to DOS2 than BG. I'm also not talking about re-used assets or a stupid arguement like 'its tha engine's fault they need to pick another engine!' (that's just utter crap, as taking a look at games using Unreal and Unity shows that engines can handle very diverse games, the differences in engines are typically not really noticible for players). I'm also not talking at all about cinematics being the issue - that's just simple zeitgeist that probably we would have seen already in BG1 and 2 if it was technically possible.