Or a parent, friend, SOCIETY, that doesn't agree with them dating. Rich person dates poor person, nope. Teacher and student, nope. Lovers that broke up but are now getting back together, but won't be together until the last page of the last chapter. Parent suddenly returns and hates them dating (looking at you Hidoku Shinaide).
Like yes these tropes exist for a reason, but we don't have to wash and repeat them all of the time. Yes I have a parent who disagrees with my 2 boys dating but it's not because they're gay, and it's not because one's rich and one's poor, it's because daddy flat-out thinks the boyfriend is not suited to be able to take care of his son in all the ways a relationship requires (namely emotionally).
I sometimes like the twists on the ex's, but only if it's not done "just to be a twist" but fits the world that was created before the ex's introduction or meddling. If it feels forced to me, or like the author was told to do this, then I'm immediately not invested anymore. (Looking at you Percy Jackson book series #3 where Annabeth suddenly is boy crazy for Percy)