What you say is correct in the sense that NWN, IWD, Torment, ToEE, etc. are more or less copies of BG which as I said with fallout 1, we popularized the genre at the time.
Nevertheless as I said implicitly baldur's gate has its own universe of dark fantasy, its own features that made him the best rpg of the time, notably the twist of the narration brought by the dreams (or rather nightmare) of the hero.
Here not having the full game it's difficult to make a final opinion but nevertheless have found the graphic and artistic universe of baldur's gate the realistic and dark aspect, at the narative level we are on a darker tone more serious and more mature than DOS 2 for example, the notion of dreams at baldur's is also included in the game.
On the other hand as you say it's not a direct sequel of the first 2 opus, but it was never announced as such but as a reboot of the baldur's saga and that doesn't mean that we can't call it baldurs gate or fallout 2 and 3 are not fallout.
Simply baldur's gate 1 and 2 were made by Bioware with their Identity, here what is reproachable on the fact that BGIII is not BG is more the fact that Larian is not Bioware, which I find sad because when we see what Bioware does today with their license what sincerely thinks that for the moment we would have had an offline solo MMO opus that masquerades the license as for the Dragon age saga that never was the height of origins.
It's just my opinion but for me BG3 as it is now is largely at the height of what the games were originally.
And change game title is just a no sens, BGIII is a BG.