QUIC would work okay, but not really have many advantages for machine-to-machine traffic. Machine-to-machine you tend to have long-lived connections over a pretty good network. In this situation TCP already works well and is currently handled better in the kernel. Eventually QUIC will probably be just as good for TCP in this use case, but we're not there yet.

You still have latency, legacy window sizes, and packet schedulers to deal with.

But that is the huge advantage of QUIC. It does NOT totally outcompete TCP traffic on links (we already have bittorrent over udp for that purpose). They redesigned the protocol 5 times or so to achieve that.