Just rushed development usually with the bigger titles. The time isnt spent on performance, it's a case of spunking a game out and moving onto the next one.
I wish I had the same luck. I have done a few play throughs (not all the way mind you) with friends and we encountered the some of the same bugs and new bugs each time. Some may be very easy to overlook and I imagine this is what a lot of people who 'dont experience any bugs' do subconciously. (You can check the patch notes for a list of bugs they have fixed and over the 5 patches, its a lot. So your curiousity can be quenched there I guess.)
However, when I enjoy a game, every little problem will stand out to me and when its stuff that exists almost everytime, then I wonder if Larian even played their own game (which funnily enough is a running joke between us since DOS2).
Yeah I got 300 hours and the game starts to fall apart in act 2 and shits the bed in act 3, bugs and loads of inconsistencies. I have never crashed either. The fact they are not just fixing bugs but adding to the story shows that there was a lot missing and the amount of QoL features that should have existed from the start is insane. Their scope was a bit too big imo and they should have kept it a shorter but more polished game.
It's a shame because the start of the game was fantastic. Like I said though, they are working through it which is good, but doesn't change the fact I bought an early access game that wasn't labelled as such.
It's an attempt at a quick cash grab by some publisher, abusing the LOTR IP and it's current resurgence in popularity. Epic Games only too. I wouldn't be surprised to hear later down the line how the devs have been on crunch to get a game out in a ridiculously short amount of time.