Just because Baldur's Gate 1 and 2 sold well doesn't mean that there's millions of hardcore Baldur's Gate fans who are super ultra invested in Baldur's Gate 3 being accurate to a niche thing like DnD.
Minor quibble: from what I've seen, the BG1 and 2 fans who are upset with BG3 are upset because it's
too accurate to D&D. They don't actually like the current D&D rules and the current D&D setting.
I have seen the exact opposite. The most prominent way in which BG1&2 fans prefer old D&D is their desire for a 6-player-party, which isn't even
that odd for 5e.
Otherwise, BG1&2 fans want BG3 to
feel like the older games, through implementing day/night, UI, resting costs, random encounters, etc. But none of these things are against the spirit/rules of 5e.
Or they want the BG3 rules to be
more like 5e rules (height, backstab, surfaces, disengage, shove, spellcasting rules, etc)
