There's easy fix for that, just set the next game in nursing home. Could be titled "Sexual adventures of senior citizens", of if you'd want something more romantic, then perhaps "True love is worth the wait".
You'd probably lose majority of your current audience, but they never paid much anyway. And with this new concept being somewhat unique, maybe you'd find hole in market and profit from that.
In any case, you'd be safe from "this character looks too young!" trolls. Well, as long as there would be no visits from grandchildren, you wouldn't show the staff much, because nurses are often young, and the story would be strictly in present time, no protagonists reminiscing about their youth. And you'd have to make sure that MC isn't struck down by dementia too much, and doesn't choose some relative of his as love interest. But other than that, it's foolproof plan.