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, slowly got their reads back.
Currently 2019 users are getting it back and it has started for 2020 users 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
Thanks a lot. (づ￣ ³￣)づ
Where's my reading lists? (╯°Д °)╯╧╧