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.
Except: I try Wayland every 6 months or so and still have problems with it.
Wayland’s problem isn’t Wayland; it’s all of the stuff that needs to work in Wayland that doesn’t. Using Wayland, to me, feels like using Windows, out a Mac: as long as you don’t stray out of the playground, it’s mostly fine (if a bit slow). As soon as you try to do any outside-the-box setup, like changing the status bar, things start getting all f’ed up. Like, last time I tried, I couldn’t get DPI font scaling to work - fonts would either be too small everywhere, or big in most apps but really tiny in the status bar. Whenever I encounter things like this, I search for solutions for, maybe an hour, see that other people have the same problem and there’s no fix yet, and bail back to X11, which Just Works.
Also, while I know some people have had bad experiences with btrfs, I’ve been using it for years. I originally switched because I had multiple separate cases of data loss using ext4, across different systems. It’s always baffled me that folks complain about btrfs, but ext4 was far less reliably. IME.
I have had the opposite experience from you with wayland and btrfs. Recent data loss with btrfs but perfect functionality with Wayland (on KDE and Arch Linux). Moving panels just works. Fractional scaling just works (though i do miss the old method where smaller screens just got supersampled instead of the way they do it now).