I don't see the point criticizing the "3" in BG3 without knowing more story details. The overarching game could tie into Bhaal's legacy in meaningful ways. The tabletop adventure that precedes this game features followers of The Dead Three of which Bhaal is a member.
Mind Flayers were already plotting to take over Faerun in BG2, perhaps the Mind Flayer in the opening is linked to that?
What we have is the first hour or so of the game that is basically teaching you mechanics. It is a prelude to the larger adventure to come. I don't see how it can be assumed that BG3 won't have enough in common with the previous two.
And at least we will actually be going to Baldur's Gate in BG3. In BG1 it took most of the game to get there, and in BG2 you never so much as step foot in the city.
