Comment by geoctl

There is actually. A way more interesting re-implementation of a popular L7 is SSH over QUIC. SSH has to implement its own mutual authentication and transport embedded in the protocol implementation since it operates on top of plaintext TCP, but with QUIC you can just offload the authentication (e.g. JWT bearer tokens issued by IdPs verified at L7 or automatically via mTLS x509 certs) and transport parts to QUIC and therefore have a much more minimal implementation.