This is a client bug, IMO. And sensible servers like Caddy (and yes, before people complain about disclosure, I made it) staple OCSP automatically.
> here's still major MITM-problems (yes, still; for example CloudFlare is huge-ass MITM),
But optional (and often discouraged), not required! Separate issue.
> HTTPS is definitely still a lot slower than HTTP, even with HTTP/2
That's just plain false across most dimensions. https://css-tricks.com/http2-real-world-performance-test-ana...
> it further makes it a lot easier to hide which data is extracted from a computer from the user
That's a separate issue too; don't use clients you don't trust, period. And some big-name clients like Chrome let you dump keys to inspect data transfers locally.
> I wish there was a way non-sensitive data could be transmitted plain-text, but signed with a server certificate.
TLS supports a "NULL" cipher in certain cipher suites for signed-only transmissions, but mainstream server and client support are limited (for good reasons).