In the core of enshittification is that there's a company behind a platform, and the company goes public and starts to chase eternal revenue growth. Eventually it will need to start finding growth at the expense of the users, say, from increasing ads, selling user data and other means that makes life terrible for users.

There's no lemmy corporation, just individuals running their instances. So yep, enshittification (in it's currently understood form at least) is not possible.

Impossible that it becomes shittified? Yes.