This seems like an unnecessarily dismissive take; I’m not terribly familiar with the emacs ecosystem but the breach of protocol in committing the change and the impact on long-standing behavior seem like reasonable objections to me.
There are a fair bit of features that are done better today than they were done decades back. Developer tooling has been getting better.
In fact today auto complete doesn't even mean what we had 5 years back, Same with code navigation. While sticking to backwards compatibility is good for your existing users(mostly older devs), that will also close the door for new comers.
This is also nonsense:
> Try using "Emacs" or even "free software" to mean something different, and see just how quickly you would hear back from Richard Stallman.
To hear from Richard Stallman, you have to use "GNU Emacs" for your fork or unrelated project. GNU Emacs is not the first Emacs. Before that there was Lucid Emacs. GNU Emacs forked at one point giving rise to XEmacs.
The GNU project produced a clone of Unix, using all the same names for numerous utilities like "ls", "make" and "grep", as well as countless API functions.
Stallman may not like it when some people use "free software" for free-as-in-beer, or else when others insist that copyleft software is not free, but he's not a gatekeeper of the English language.
Someone else is almost as crazy is not a good justification.
Here's a timeline of Emacs https://www.jwz.org/doc/emacs-timeline.html