Quite frankly I think that if Larian won't address this issue is because they just don't want to, because they are too stubborn about the alleged merit of their own Frankenstein creature and, as KingNothing said, they don't want to "kill their own darling". Not because they are facing any meaningful technical limitation.
True... one might think that, at some point, the "limitations" of their engine might have reached a point where they though: We just can't do this title justice with our tech... but apparently not. The game is definitely worse of for that. Clunky party movement, no formations, no day/night cycle, no optional RTWP, maybe even the horrendous inventory,... all those seam to be due to what the engine is capable of.