No. They have that data forever. You can’t take it back.
Who knows what’s going to happen to it in 20-50 years, people never seem to consider those timescales when handing over their data to companies.
Worst part is, there is a solid chance they already have all your data from a sibling or close relative.
Before people get worried about this, this is how literally any online service works. If you have an account anywhere, you trusted that service to not record your password.
Only exception is oauth, which actually might be a good idea for Lemmy.