Gmail is not "crippled". A tiny but vocal community of old nerds have a petrified mental model of email that they associate with unix IMAP software from the 1990's, but those concepts do not appear in the IMAP standards anywhere.
For context: I spent 11 years at Intel managing pre-silicon and post-silicon processor validation. No processor that does only and exactly what the Programmers Reference Manual says, and takes the phrase "undefined behavior" seriously, will be successful. Google would do well to adjust their philosophy.
It's really dumb that one message has* to exist in only one location for example, labels are so much better.
The standard document may say one thing, but what people do in the real world is the real standard. If your software has issues with the world's most popular IMAP server, you need to adjust your software to be compliant with the standard.
I'm personally more sympathetic to your actual conclusion, but it's odd how often a single argument can be used to support two conflicting beliefs.
Certainly I moved away to Fastmail, which has better IMAP support (but mostly because Google having full control of my email address was becoming too big of a risk and Google Apps is expensive for your own domain).
To be clear, I have no opinion on IMAP or what things _should_ do; I certainly was not using IMAP software in the 1990s :) However, trying to implement a client that works across providers does mean trying to operate per the standards, which was a struggle and why I started documenting it :)
When was OBJECTID introduced and when did gmail roll their own implementation, do you happen to know?
RFC 9051 says that it was "developed for" RFC 822 and that one should now refer to RFC 5322 instead. And RFC 5322 does discuss threading, which is the what the comment you're replying to was talking about, so that concept does appear (by reference) in the IMAP standards.
Are there other parts of the community that implement IMAP using the same "mental model of email" that Gmail is using? Or are you saying that anyone using IMAP with anything but Gmail is an old nerd and a tiny minority?