[overgard]

It's very true; I remember one game I was working on, when you pulled down the code and new assets it'd take a long time to rebuild the "Library" (which is not something you can check in). And sometimes, if your version of the project was acting wonky and everyone else was fine, the solution was to delete the Library and rebuild it from scratch. If you were doing it from scratch, it could take hours. They've made some improvements but it's still a mess.

The editor itself always seems very buggy. If you have the "Console" open (which you will if you're coding), it's pretty much guaranteed you're going to see a lot of random errors that have nothing to do with even your code. A lot of them don't even make sense or could be ignored. Like you'll get weird asset import errors if you upgrade versions, but a lot of times they're just red herrings and not important. There's also a lot of QOL stuff that's very frustrating, like arrays being annoying to edit (I'm not sure if they've fixed this yet or not). It's also easy to accidentally brick your editor on your own, with debugger shenanigans or loops that don't end.

Also, if you're trying to build a an editor extension, omg was that a nightmare. Just getting things like Undo/Redo and object serialization working correctly are difficult and in some cases impossible. And frankly, you need extensions for a lot of things to actually be useful, like until recently the builtin terrain editor was basically useless, and you have things like Odin because the builtin inspector is a nightmare.

There's a lot to like about Unity, but there's also a huge amount of pain points with it.