I am making a guess, but I wonder if a non-Baldur's Gate game would be able to get such a big budget. BG is a flagship IP, so even though Larian is more interested in expanding their D:OS formula, it might have greatly controbuted to funding.
I find Larian's storytelling wanting. Their games feel to me more like sandbox or themepark then an interactive story or adventure. Wealth of interactivity and reactivity doesn't mean anything to me, if I am not drawn into fiction. Having choice is unappealing, if I am not concerned about outcome. I really dislike Larian's coopcentric design - Origins I think are a horrible abomination resulting in not interesting companions, and reducing our ability to shape our custom NPC when deciding to go that route. I am doubtful if Larian's commitment to high fidelity presentation will pay off. What we have so far, I think is awful, but with game not being finished yet it is difficult to say how it will look.
And then there is weird stuff - taking rest teleporting you to a pocked-universe camp in a generic woods, quick travel teleport, singular map design which doesn't try to create a coherent locations (people unaware of what is happening outside the zone they have been designed for - think Driftwood citizens from D:OS2 unaware of a massive hole in the ground a minute away from their town).
I will am not hang up on any individual changes (being made by Larian, I did expect to get Larian game) but I am doubtful. When it was announced I thought: "Larian game using DnD setting and ruleset! I can get behind that", and then Larian seems to try to gut DnD and make it as close to Divinity as they can - missing is rare due to overabundance of advantage, guaranteed source of damage through surfaces, broken action economy. It's not even D:OS2 vs DnD - it's just both work so differently that I think Larian is in danger of satisfying no one. But they still have time to itirate. I do hope the changes he is talking about will attempt to fix at least some problems (like reactions).
I don't really judge BG3 against BG1&2 - I see Larian games as a completely different genre then Infinity Engine games, though I wish they had a different sense of humor. I find their games rather unfunny. Then again, I didn't like D:OS2 much. In fact, I thought D:OS1 was a better title. I do think that BG3 will be better then either, and BG3 definitely tries to address at least some of the criticism one could level against D:OS2 (companions are way more fleshed out for one), but it still doesn't just click with me.
My datailed thoughts on each are here and here.