Artists literally cannot do anything.
To simply change an album cover, first you have to submit a request with your publisher. If you're on good terms they'll get to it in a reasonable amount of time and reach out to Spotify. They'll review it if its actually acceptable and decide if you'll be censored. At some point a month or so down the line, the album cover will change, you might get an email.
Imagine if there was an alternative network where you can just permissionlessly click upload cover art, hit save, and be done with it.

