I generally agree that comparing both games is kind of an exercise in futility, but it's not exactly what's happening in this thread, so I don't agree with your overall argument. People are largely comparing combat mechanics, which is the one common topic shared across both games, and comparisons are naturally going to happen when both games are supposedly adaptations of the same source material.
You could argue that BG3 shouldn't have stuff like proper reactions because it's supposed to be cinematic and immersive, but that's a flimsy cop-out bottom of the barrel argument at best, because chances are extremely high that's not actually why we don't have things like reactions, ready actions, and dodge actions to begin with. Features are generally cut due to budget constraints or engine limitations, not because 'they don't fit developer vision'. If the latter reasoning actually is at play here, I'm pretty sure we would have heard something about it from Larian by now.
I'm quite sure if one tried justifying that kind of reasoning for the lack of reactions even at the BG3 subreddit, no one would accept that argument, even if that place is infamous for being an echo chamber that generally worships everything Larian and harasses anyone with any kind of criticism without a second thought. Most people would definitely prefer greater choice and control over such a highly subjective concept as 'immersion'.
It's a poor argument when one considers that BG3 combat in itself is already as non-immersive as it gets. Because if one is really trying to pin the lack of certain key combat features on such a vague concept as cinematic immersion, they should also be prepared to try and justify things like freely sneaking around and dropping barrels while all nearby combatants are unable to retaliate, for the sole reason of one player character that has rolled initiative purposefully twiddling their thumbs. Is that supposed to be a legitimate cinematically immersive experience?
(Do you know what actually was a major mechanic brought about by developer vision? Dim light disadvantage in Solasta, which the devs there publicly walked back several months later when they realized that it had an overwhelming effect on the game's encounter balance and actually clashed against the rest of the game's vision of being as faithful to the source material as possible.)