A really good combat-oriented DM will keep your party on the edge of death most of the time. It's what makes things exciting.
What BG3 really needs is a better set of tooltips to ease players new to 5e or players coming off of DOS2 into the system. Really emphasize Advantage vs Disadvantage, how the action economy works, guiding them into abusing the environment and the effective ways to combo with the party. Basically, use everything, unchain your party frequently, scout effectively, know how reactions work (how to intentionally trigger them, how to deflect them, how to prevent them), and use the right Action vs Bonus Action at the right time.
My observations from the forums and steam is that players familiar with tabletop are doing quite well, players from DOS2 have the right ideas but aren't familiar with the spells and systems enough to put them to use effectively, but players from BG1 & BG2 are really struggling because they're still used to the 2nd Edition rules and balance.
You make a number of good points here. The first is that I would steer clear from combat-oriented DMs. I come to TTRPGs and indeed cRPGs for roleplay, not combat and in cRPGs in particular the combat tends to be the aspect I'd be most willing to part with (not that it can't be good or enjoyable, I love turn based combat in Pillars of Eternity: Deadfire).
Also you're articulating a point that I haven't been able to properly articulate myself; the game needs to teach its players how it expects to be played. If it's going to expect players to make such high level use of everything at their disposal then it needs to be better at communicating that. Putting players in situations early on where creative, out of the box decisions are obvious and straight forward charging into combat would be suicidal. As well as teaching players all the systems you mentioned. Because I'm playing like I would play a standard cRPG on normal mode, where you can get through most combats by brute force with deeper system mastery needed for bigger challenges and boss fights.
