It doesn't. Witcher1&2 got Enhanced Editions, Witcher3 didn't. And it wasn't because CDPR cared less for Witcher3 - it just launched in a much, much better state and didn't need to be rebranded and relaunched. Than Cyberpunk77 came out and it also needed a bit 2.0 rebranding. I do sincerely hope that Larian won't follow the same route, and their next game won't need a relaunch a year of two after it was "completed" for the first time.
Larian has been supporting BG3 for what will soon be a year. Which I think is about the same as they did with D:OS1&2. I mean, I don't even like BG3 that much, but it is bizzare to me that some bring D:OS2 as some kind of beacon of Larian commitment and perfection, while BG3 on launch was so much more ambitious and in such better state than D:OS2 is now. "They remade D:OS2 act3" might seem like a lot, but not when you compare it to what an act means in BG3. If they are working on polishing what they have, that's probably a better time investment, than creating new content that would release with it's own host of new issues.
Yes, Larian designs overambitious 1st act, spends time in EA to test and improve on it, and rest of their games feels like a let down afterwards. That's, I am afraid, a downside of how they develop their games. It gets better everytime, maybe one day they will figure out how to keep the quality up for the entire title.
The Witcher 3 got two huge dlcs. Each one had enough content to be a small game itself. Blood and Wine came with a new world and the conclusion of the main quest served as a true ending for the saga. The "Complete Edition" of the game includes the dlcs. The game has also been updated for years with new free content, including new scenes and story content. They added in whole romance scenes because people were unsatisfied. And the most recent "next gen" major free update included a whole new story quest, a small explorable area, minor side quests and items, a romance scene, etc.
So I would say The Witcher 3 undoubtedly got even more care post launch than the previous two games, despite being superior to them when released.
People are bringing up DOS2 because as you said BG3 followed the same pattern with the drop in quality at the end, but they've decided to leave it as is this time. I don't think it matters that BG3 started in a better place than DOS2. The point is that Larian made the same mistake but this time they don't care enough to do what they've done in the past to rectify it. Their future games may be better, but that doesn't change anything for BG3.
I would also say talking about an explorable area of the game a month before release, and then publishing a video where they talked about it again two weeks before release, indicates that something happened and it wasn't simply content they decided to scrap during development. They've talked about content that they cut during development like Ketheric being a potential companion, avernus being an explorable area, etc. But they've been vague about the upper city and only said it was meant to be explorable in their original scrapped epilogue.
