I disagree. There is plenty of ossification coming from inside the house. Just some examples off the top of my head are the stuck-in-1974 minimum RTO and ack delay time parameters, and the unwillingness to land microsecond timestamps.

The "middleboxes" excuse for not improving (or replacing) protocols in the past was horseshit. If a big incumbent player in the networking world releases a new feature that everyone wants (but nobody else has), everyone else (including 'middlebox' vendors) will bend over backwards to support it, because if you don't your competitors will and then you lose business. It was never a technical or logistical issue, it was an economic and supply-demand issue.

To prove it:

1. Add a new OSI Layer 4 protocol called "QUIC" and give it a new protocol number, and just for fun, change the UDP frame header semantics so it can't be confused for UDP.

2. Then release kernel updates to support the new protocol.

Nobody's going to use it, right? Because internet routers, home wireless routers, servers, shared libraries, etc would all need their TCP/IP stacks updated to support the new protocol. If we can't ship it over a weekend, it takes too long!

But wait. What if ChatGPT/Claude/Gemini/etc only supported communication over that protocol? You know what would happen: every vendor in the world would backport firmware patches overnight, bending over backwards to support it. Because they can smell the money.