All 3 means of installation (Jetbrain's app, snap and potentially apt) are one-liners for the end-user. So, ease-of-use is hardly a compelling argument.
And I don't question your initial assessment about other applications in the archive. Hence myself mentioning eclipse earlier, as a similar package which used to be actively maintained until the effort died out.
I am just wondering whether an effort to package pycharm would not reach the same outcome, assuming it passes the initial import phase. The Atom IDE for instance never did.