Check your admin control panel and turn off anonymous editing. But keep in mind that this is will only delay them by half an week or so. You'll probably might want to look into permanently locking some pages...But then someone might start bitching at you because it goes against the "spirit" of running an wiki, but that's life

Do you have a rules system set up for the wiki? If so considering adding a rule that users need to have reference links to back up what they are adding to a page. That could help minimize arguments and edit wars.

You can try emailing Fandom support and ask that they switch the wiki to autoconfirmed users only. This will only stall the new accounts for 96 hours, but that's better than having to deal with it every single day. You can also check with Fandom support to see if there's any additional support that they can provide you. support.fandom.com/hc/requests/new