At core, it's just request-reply + key-value metadata. Whenever it's text, or binary, it does not matter much. But writing HTTP/2 frame types in letters would not make them any easier to understand.
Now, HTTP/2 isn't even conceptually simple, I agree about that... it seems ugly.
well because the hard part is the client-side. caching is a client-side only thing with http, keep-alive is a thing that a server pushes to a client, the same with chunked transfer, which is not as easy to implement for a client like it was with content length.
basically a server does only need to implement certain headers, but a client needs to know all. also most clients even accept bad servers, like content for head requests, etc.. most stateless protocols put a lot of burden into clients.
h2 on the other hand is stateful and keeps the same hard semantics onto the client side and also makes servers more complex, because it's a state machine.
While '408 Request Timeout' is somewhat dubious fig leaf over TCP RST