But the whole point of QUIC is that it is a userspace implementation. From the QUIC viewpoint (and I take no sides in this) kernel implementation is death for a protocol because it freezes its specification and behaviour in slow-to-update systems. This is why they found they couldn't "just improve TCP".
I get why Google, which controls a great deal of the software on both ends of a very large number of connections, finds a settled standard inconvenient.
But from my perspective, as somebody who uses Google software but does a lot of other things too, I like when we have standards that are implemented by many different people and aren't controlled by a single vendor that is eager to maintain or extend their large market shares in many areas. Can that be slow to change? Sure. But the speed is proportional to how much the change benefits people besides Google.
Personally, I hope that QUIC is a first step toward taking the lessons learned and implementing them widely, rather than something that will evolve at a rapid pace precisely as long as Google needs it to and then stop.
