RE: Network Attached Storage (NAS) 2024 Series - 2

This goes into great detail about it.

Short answer:
It really isn't tuned for it, when ZFS was created there was only rust drives, so there is overhead (queuing, locking, syncs) that isn't a big deal when you have slow rust, but with nvme they add up a lot.

You can tune things to run a lot better, and the guys in the video above made a custom patch to really tune it.