I currently use btrfs with RAID1 at home, and it works great. But btrfs also does not have the track record for being the most stable filesystem as compared to ZFS.
You can do that with ZFS too, at least for mirrored sets (i.e. RAID10). It's possible to remove a vdev, and the pool will migrate the data to the remaining vdevs.
[1] https://lore.kernel.org/linux-btrfs/20200627032414.GX10769@h... [2] https://lore.kernel.org/linux-btrfs/20200627030614.GW10769@h... [3] https://lore.kernel.org/linux-btrfs/20200520013255.GD10769@h...