Last I heard (~8 years ago), the RAID-like functionality in btrfs was very unstable and crash-prone. The impression I got was that there was not a lot of interest in fixing this. Then bcachefs came and ... appears to have gone nowhere AFAICT.
The non-RAID part of btrfs appears to be stable. It's the default filesystem on openSUSE and SLES. But I don't think it's ever going to reach feature parity with ZFS.
And to the grandparent post's point, since the split with the kernel there've been two big new feature releases: reconcile, which puts our data and drive management head and shoulders above other filesystems - and erasure coding was just released, 1.37 came out a few days ago.
The non-RAID part of btrfs appears to be stable. It's the default filesystem on openSUSE and SLES. But I don't think it's ever going to reach feature parity with ZFS.