It already exists, it's called SCTP. It doesn't work over the Internet because there's too much crufty hardware in the middle that will drop it instead of routing it. Also, Microsoft refused to implement it in Windows and also banned raw sockets so it's impossible to get support for it on that platform without custom drivers that practically nobody will install.
I don't know how familiar the developers of QUIC were with SCTP in particular but they were definitely aware of the problems that prevented a better TCP from existing. The only practical solution is to build something on top of UDP, but if even that option proves unworkable, then the only other possibility left is to fragment the Internet.
I like (some aspects of) SCTP too but it's not a solution to this problem.
If you've followed Dave Taht's bufferbloat stuff, the reason he lost faith in TCP is because middle devices have access to the TCP header and can interfere with it.
If SCTP got popular, then middle devices would ruin SCTP in the same way.
QUIC is the bufferbloat preferred solution because the header is encrypted. It's not possible for a middle device to interfere with QUIC. Endpoints, and only endpoints, control their own traffic.
I don't know how familiar the developers of QUIC were with SCTP in particular but they were definitely aware of the problems that prevented a better TCP from existing. The only practical solution is to build something on top of UDP, but if even that option proves unworkable, then the only other possibility left is to fragment the Internet.