I think any discussion of btrfs needs to acknowledge that raid5/6 support was promised in the early years, shipped in the kernel in 2013 and, until 2021's btrfs-progs 5.11 release, did not warn users that they risked data loss when creating volumes.

For near a decade btrfs raid5/6 was "unsafe at any speed" and many people lost data to it, including myself.