I don't even care about how faithful BG3 may or may not be to the core DnD rules anymore. I came to realize over the past few months that I cared far more about how imbalanced the game is in general at its very core, and not about any comparisons between BG3 and the actual tabletop rules themselves. It just so happens that the vast majority of mechanics that contribute towards this feeling for me are the homebrew mechanics and changes that were haphazardly shoved into the system anyway.
I can also see how a fair amount of people that are arguing from the faithfulness angle may feel rather miffed, if not insulted at how BG3 has handled things. One may bring up how the RTwP games aren't faithful at their very core, but that's something easy to accept because of how obvious it is and that the developer vision is very clear there (and that most people's standards of balance are a lot more lenient when it comes to more action-based games, since there's a lot more moving pieces compared to a turn-based game). But BG3 somehow took a ruleset that was already turn-based to begin with, and transformed it into a highly imbalanced version with a lot of custom mechanics that appear to be designed around the idea that you should avoid engaging with the more faithful mechanics as much as you can, lest you get slapped with penalties that didn't exist under the base system. To make matters worse, there were some rather unflattering interviews earlier on that some have interpreted as Larian mansplaining to fans of the base system about how the rules can't be translated to a video game format in a 'fun' way, to the point where I now wonder if Larian is right to keep their mouths shut as they have been lately to avoid such additional blunders.
Still, it takes an awkward amount of effort to pull off something that so systematically neuters the base mechanics so much, that prior knowledge of DOS mechanics would generally serve you far better than prior knowledge of the DnD mechanics in BG3.
Most hardcore turn-based enthusiasts would have absolutely already ripped BG3 a new one if it didn't have both the BG name and Larian's name attached to it. Would people have found things like high ground advantage/disadvantage acceptable within any other game such as Solasta? Considering how people were right to argue about how bad dim light disadvantage was in terms of having far too much of an influence in decision-making during the earliest parts of that game's EA period, definitely not.
I mean, I don't think people are generally hostile to homebrew mechanics - Solasta is literally far more homebrew than BG3, after all, the difference being that they had to homebrew their world and subclasses while leaving the actual combat mechanics largely untouched. But the majority of BG3's homebrew mechanics are just bad by all metrics, faithfulness or not. Barrelmancy? Fine, I actually don't care about that. Backstab/high ground advantage and low ground disadvantage? That's not interesting at all, they just force a specific playing style and limit rather than expanding options.
Even so, I think people should really stop trying to use the faithfulness to tabletop arguments. It means nothing to anyone not familiar with the base rules, and it lets people reduce your arguments to ramblings of rabid purists. But argue from the standpoint of the balance and mechanical design on their own merits itself, and most of the gaming public would understand. Larian would probably be forced to listen if BG3 were to suddenly gain a reputation as a game with impressive visuals, but with a combat system that people can meme in a really reductionist but accurate way - the three major solutions of high ground, backstab, barrelmancy.
I almost wonder if bonus action shove and jump actually only exist as an over correction to high ground/low ground advantage/disadvantage. When you really think about it, almost all of the game’s questionable design can be traced back to that very mechanic. Without bonus action shove, entire fights would be taking place at the summit of a mountain. Without bonus action jump, reaching that summit becomes much harder. Backstab likely only exists to give melee an answer to ranged having high ground advantage.
I came to this type of thought during a mental exercise, wondering who would win in a fight between a BG3 party and a Solasta party. The latter would probably win handily, not only because they had access to proper reactions, but because the BG3 ranged characters would get screwed over by their very own low ground disadvantage mechanic the very moment the Solasta party gets to high ground. Maybe it’s the reason proper reactions aren’t a thing either - a wizard with Shield would effectively be untouchable to anyone on low ground.