Ok, with (1) Clear instances where it would be a problem would be the level of trust. So a 16 year old is likely to place a lot of (possibly misguided) trust in a 50 year old partner. It think that’s where a lot of the “dirty old man”/“cradle snatching” comes from. It’s not wrong to be attracted, but the relationship does raise issues.
With (2) I have no problem morally. The idea that two cousins having a baby with a medical condition being because they are cousins is ignoring the point. They are two people with particular genetic material. Just as cousins with a family history of thalassemia could have a kid with it, there’s a chance any couple of Mediterranean background runs a risk, too. It’s not like God/Cthulhu is punishing someone for crossing the line we have created.
In both cases, the problem is reproduction. An older mother or father may cause pregnancy complications or affect the development of the child. Shared genetic factors may do the same for a blood-related couple. So I guess you trust people to know what’s right for them and to consult when they need guidance in these areas.
Just representin’ the inbred folk here.