They aren't deleted you'll get them back.
don't worry, ppl whose acc were made in 2014 and 2015, as in earlier years, they're slowly getting their reads back. Here's some proof, also rn 2016 users are getting it back too
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 had like 5000+ saved in total. Both to Read, as already finished. And all those who I want to read, is also gone. I fortunately have my bookmarks intact. But sadly didn't bookmark everything. Someone at comments said we might get our list back. But who knows for how long. We won't get any notifications when list is empty. (〜 ̄△ ̄)〜, I have to get some of my bookmarks to put back on the list at least.

MY READING LISTTT _:(´ཀ`」 ∠): does anyone know if it will fix itself? I had over 1000 saved and now it’s all gone, however my personal lists are still good for now