What FanFiction and AO3 need is a “suggested story” list. When you finish one fic you really liked and you now need to fill the void, you just click on the option and find a similar one.
Hi there! Share what you're reading? Go to your AO3 history and see if there's anything you've read recently that you've liked. Left kudos? Left a comment? Awesome! Now go the last step and give us a rec! (Tag the author if you can!) Then pass it on!