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.
@lancalot @possiblylinux127 I tried it once, it pissed itself and corrupted the entire file system to the point where I couldn’t recover, went back to ext4. Had similar experience with xfs.