> clojure-mode is an existing package with thousands (tens of thousands?
> millions?) users and certain existing functionality. Other (also
> third-party) packages rely on it for various functionality. It's not a
> bare-bones major mode with basic functionality only.
This underscores my point: clojure-mode is an important feature, so
Emacs should provide it. It should be a full-fledged part of Emacs,
documented in Emacs. To leave these jobs to nonrecommended add-ons,
such as found in NonGNU-ELPA, is not doing a good job.
We hope that Emacs users who write extensions will appreciate Emacs
enough to contribute them to Emacs. Usually they do. When they
don't, that's unfortunate -- but we can make up for it. It isn't an
lot of work compared with all the work we do on Emacs in a year.