Firstly the complaint that Larian isn't using D&D RAW and creating house rules.
I never played actual D&D (only it's PC adaptations) and I am fully supporting making changes to the system to make it better on PC. That said, playing BG3 demo, I found combat to be pretty repetitive and boring. From what I understand some complaints I
had are a result of changes to the core rules, which undermine original systems. It's not that changes are bad, it's that bad changes are bad.
Secondly is all the complaints about BG3 just being DOS3. DOS was obviously Larian's way of making a D&D like game in the first place. Party-based, pseudo-medieval with story and narrative elements tied together by many combats. Basically D&D.
Yeah, I don't like this complaint as well, but mostly because it's very vague. It is clearly not D:OS3 - there are many differences one can point to. But at the same times D&D can mean many things - Neverwinter Nights1 is arguably a better D&D adaptation then BG1&2, but I actually quite disliked NWN, while I loved BG1&2. The point really isn't what BG3 is or isn't, but that there is a substantial fanbase of BG1&2, who don't like Larian's take on the IP. Whenever it is relevant or not, is up to debate as long as there IS an audience for BG3. I personally found what I like in Pillars of Eternity series, while other Infinity Engine fans dislike it. I think that Kingmaker is hot garbage, while others praise it as 2nd coming of BG. It is somewhat unreasonable to expect for Larian to make a BG3 and satisfy absolutely everyone. At the same time, Early Access is there for us to complain, so as a fan of BG series I don't like something, why not to voice it?