And the other part of the problem is that Larian doesn't want to make a Baldur's Gate game.
They want to tell a story in the Faerun universe, which is awesome, but they want to just use the mechanics of DoS. And I would be 110% in support of that....if they wanted to call it something else. Because yes, calling it BG 3 means they are taking advantage of one of the longest lasting and most active cRPG communities to ever exist. All the work of the Enhanced Editions, mods, ports, forums, etc that kept a game alive and continuing to receive numerous top ratings and popularity.
They need to decide what kind of game they want to make and announce it to the world. Either they're making DoS 3 and just using the setting of Faerun, or they're making a game in the same spirit as the Baldur's Gate series. I'd be happy with either, but right now they're trying to split the difference and failing at both.