You sign up for a website and upload and share a bunch of memes.... honestly... the shit isn't really your data anymore. It is the publics. You shared it and yanking it back is kind of a dick move.
It really isn't as "simple" as a DELETE statement that some people argue it is.
As for personal info, most meme websites don't require any accounts to create them, because it only makes the site less usable, but if the site do have accounts, you do have right to see/update your account, you have right to delete your account and be sure that if your account is deleted the data is actually gone.
Very generous assumption on your part. Article 9 specifically says that anything revealing personal info like ethnicity, political affiliation, etc. is covered by GDPR. If I look at a Adam's list of authored memes and there's a bunch of pro-Democrat memes and I look at Bob's and it's all pro-Republican memes, then it's very easy to see a court ruling that a memes reveal political affiliation.
Themselves
> build a system to purge user data
SELECT * from users, memes, usermemes where userid = #####