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.
And there is were the community has kind diverged. Now days it is either headless servers or desktops.
Running individual apps is interesting but I am afraid that it is not super practical in 2024. However, there is this: https://github.com/udevbe/greenfield
Xorg is no longer being maintained for the most part and because the code base is so large there isn’t anyone who understands the codebase. I still use it for my semi virtual PC as Xorg allows for a lot more flexibility than Wayland plus Xfce4 isn’t completely ported yet. There will be a day when I move completely though. Probably when Xfce4 is Wayland native.