Which is why using BG3 as a marketing ploy might be considered impolite
Absolutely. I agree. Calling it BG3 is so obviously a marketing ploy. BG3 has no relationship whatsoever to the first two games other than the use of the namesake city.
And as for the game's imagery, just go take a look at videos and trailers for Solasta. Solasta looks very much like a game set in the Forgotten Realms even though it is in reality not. Solasta's budget is a tiny fraction of BG3's huge AAA budget, and yet looks so much better and so much more like a true D&D/FR game.