I think the exact opposite is true in reality, people want to nimbly implement protocols so badly they'd rather shove everything on top of UDP/TCP or even HTTP than deal with waiting around for whole operating systems to age out. From a pure technical design standpoint I agree a lot of things should be done at lower layers but I don't think it's possible for this to happen as quickly as a lot of people are wanting.
Not to mention the second travesty of the layered protocol model in the real world: hardware and configurations have started to grow around it. A lot of networks can't handle QUIC simply because UDP 443 won't go through their firewall yet people are expecting everyone to just jump up and start NATing completely different L4 protocols? Remember IPv6 has been around since the late 90s yet people are still sticking to the same NAT solution.
Became more rambly than I wanted but I'm just a network guy frustrated that we can't keep building up the protocol stack nor can we tear it down.