You could marry a perfectly healthy person and they will become violently sick a day after the wedding. So plans to marry perfectly healthy people might not be realistic.

Personally I’d not marry someone who doesn’t see their doctor, isn’t in treatment, doesn’t monitor their health, does not keep regular appointments: physical, dental, mental health if needed, neglect their health, doesn’t maintain health insurance etc It would not work for me. Big red flag.

If they have issues but monitor it closely, maintain routine health appointments and seek help etc that I can live with.