they aren't deleted you'll get them back for sure!
don't worry, ppl whose acc were made in 2014 and 2015, as in earlier years, they're slowly getting their reads back. Even ppl whose accs were made in 2016 are getting their stuff back rn -
https://www.mangago.me/home/people/65330/home/
https://www.mangago.me/home/people/7934/home/
https://www.mangago.me/home/people/12004/home/
so yeahh it'll take quite some time but you'll get them back.
also once they're back, in case you're looking for ways to save them perhaps in an excel file, I've made a tutorial on how to do it easily and quickly rather than having to enter everything manually one by one, so if you'd like, you can check it out.
https://docs.google.com/document/d/14Drj0CviUhrAmZlU-DC-AtxGFQoH1_PYQ81b2Vzu82w/edit?tab=t.0
I haven't tried this since I was lazy to do it but here: https://www.reddit.com/r/mangago/comments/pdflgv/script_for_backing_up_reading_lists_v10_release/
It's like an extension that will back up your lists.

if my reading lists come back i’m saving that shit in my notes app