And even then, sometimes it does work out (and I mean that in the most exceptional of cases) where there's consensus and understanding but even when it works out, it's weird as fuck for years to be friends with that couple.
Second-hand experience (my acquaintances): a 35-year-old and a 20-year old. It's outright grooming on the guys' part, if not unintentional (that is, not specifically targeted) but that guy is having real problems with relationships with people his age. So he kept changing his girlfriends and aged but his girlfriends' initial age didn't change.
What I'm saying is, even the fringe case display an older partner's inability to compromise and co-exist with an equal or stronger personality, thus they are looking for a mould to create a perfect wife for themselves. Creepy and outright pedophilic. But one of the grey area cases (or maybe I'm biased because they are my acquaintances).
Publicly saying that you want to stuff 16-year olds with cock. Forget it. Face the wall. Frankly, I'd get my acquaintance to jail to be fair.