"First, HTTP/1.1 is only simple if you're not proxying."

Which is to say, proxy implementations are complex, not HTTP/1.1

"HTTP/2 is not perfect - it's significantly more complex than HTTP/1, and can be painful to implement."

Which is to say, HTTP/2 is complex

Making life easier for (overly) complex proxy software by introducing a more complex protocol

Sounds great

Increasing complexity will surely lead to "a secure web"

I had heard rumors of this being much worse than I am understanding it. This looks like desync attacks on misconfigured proxies. These misconfigurations are normally assumed benign - which is a problem - but this is nothing all that surprising to me.