No one is saying the new game is bad or shouldn't be made, but it is not "BG3" in spirit, it is only BG3 in name.
I don't really think the distinction is important unless you're a raging fanboy and raging fanboys can rarely be pleased, so since Larian just can't win you guys over it's only logical they shouldn't even try. I did like that story about childhood shower time, it was a pretty spot on allegory to you guys, hah.
Ok so if distinction is not important. Why don't they call it "Baldur's Gate : ..." ?
Marketing reasons. I'm fine with that and I suppose most people are. It's just a minor but apparently very vocal group who have apparently elevated Baldur's Gate into an abstract concept that when messed with will bring their wrath upon message boards all over the internet, hah.
If the game is bad, you don't have to play it. I haven't read the Dune books written after Daddy Herbert's death, but they take nothing away from my enjoyment of the originals. I just pretend they don't exist. Then again I enjoyed Fallout New Vegas and NWN2 despite both being sequels with fairly little in common with their predecessors.
Then again I'm not a self proclaimed GAMER nor a fanboy, so maybe my mature view of these things is unfathomable to you.