I think the problem with btrfs is that it entered the spotlight way to early. With Wayland there was time to work on a lot of the kinks before everyone started seriously switching.
On btrfs a bunch of people switched blindly and then lost data. This caused many to have a bad impression of btrfs. These days it is significantly better but because there was so much fear there is less attention paid to it and it is less widely used.
I had to switch to X after upgrading my system because it was all choppy on Wayland. I spent a few hours trying to figure out why and then I said fuck it, X still works. Wayland still is an unfinished mess.