No, protocols directly on IP specifically can’t be used in userland because they can’t be multiplexed to multiple processes.

If everything above IP was in userland, only one program at a time could use TCP.

TCP and UDP being intermediated by the kernel allow multiple programs to use the protocols at the same time because the kernel routes based on port to each socket.

QUIC sits a layer even higher because it cruises on UDP, so I think your point still stands, but it’s stuff on top of TCP/UDP, not IP.