Also a thing I have in my DnD setting is that someone’s personal image of themselves plays a role in regeneration

For example let’s say someone who is blind has fully accepted it about themselves and someone for some reason needs to cast regeneration on them. It wouldn’t restore their eye sight because they have embraced it as a part of themselves.

In the case of the blind man the party met they were blind for decades, they had fully accepted it about themselves. Not even bringing up the difficulty of getting to the point of knowing (or finding some who knows) Regeneration (a very very powerful spell) he had no use for sight in his mind. He lived his life as fully as anyone else. It was a part of him. So if someone cast Regeneration to save his life he’d still be blind.

Spells affecting willing creatures is a funny term in my eyes. Willing can be “willing to a point” is as valid as fully willing.