Regrettably, what you’re saying is probably true, which frankly hurts even more than there being some behind the scenes drama, because frankly it shows me that despite all the praise they’re getting, the Larian crew is immensely lazy in spite of their incredible talents. It’s super unfortunate that a game as good as this would be left in a state that frankly feels like a draft for a project before it’s final copy is put together (it’s still like the best draft for something that’s been put together in a long time). We as a community really should be giving larian more backlash for this honestly unacceptable stance on game development, but it’s inevitably drowned out by the praise for all the good parts of the game that do deserve praise.
My personal conclusion is to simply speak with my wallet in this scenario. I have no plans of buying larian’s next project until at the very least a definitive edition comes out in the future. I don’t want to be treated like a beta tester for a game when it’s advertised as the final release, and then just left in the dust because the developers realized that it’s just too much work to actually commit to crossing the finish line. Theres plenty of other rpgs out there that have much weaker writing, characters, and gameplay, but at least they don’t leave me in a place where I think “Man it’s like there’s entire chunks of the game that just straight up aren’t there that are supposed to be”.
I would say it's burnout and eagerness to work on something new rather than laziness. They're clearly very passionate about their work and it shows in the parts of the game that are great as you said.
But it's... I'm not sure how to word it. I think the project should be worked on until it's truly complete despite how excited they may be to start something new. They knew this with dos2 but they're content with leaving BG3 with a middling conclusion. It's not about wanting new content for the sake of it. I would never say The Witcher 3 was abandoned when it ended because the ending was beyond satisfactory. But BG3's final act isn't. So I would say it's been abandoned.