Quic still relies on UDP, just like many other non-TCP protocols that are built by vendors for all sorts of applications.
QUIC uses UDP but not in a "it's relying on UDP" way as much as "layering UDP allowed it to go through middleware boxes" way. The developers of QUIC would have liked QUIC to not depend on UDP, and the protocol works fine that way, but then it wouldn't have went through home routers or corporate firewalls very well. Regardless a lot which used to be done in the OS TCP stack is now handled by the browser application. This is similar to how some other apps have used UDP but that doesn't take away from that fact.