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.
It is not trying to be a one to one replacement. It is a totally different thing. You are wanting a motorcycle to replace your 2002 pickup truck.
Also X forwarding is broken for most stuff. It probably will work but it will run poorly and use lots of bandwidth. This is because there are layers and layers of work arounds to make modern hardware and software work on it. The X protocol was intended for mainframes in the 80’s. It should’ve died long ago.