Not defending them at all here but there’s no compelling reason for most users to change when discord works and it works well
I understand this but it's also a little "There's no compelling reason for us frogs to get out of this water. It's warm and comfortable". It's inevitably going to boil.
But you're right that there aren't great alternatives (that I know of). I think matrix is out there, but I don't know anyone who uses it.