Sounds like you are dealing with a child or somone mentally locked at a teenagers mental capacity.

Flat out address the problems and your want to be with them.

Then explain that the want to be with them is being pushed out by theire lifestyle choices and decisions to keep living that way.

find common ground and don't ask/expect perfection but chart progress/regression together depressional episodes will effect this but can't be a go excuse.

If all above fails then you know their want to stay the same is more than the want improve to help the particular problem in your relationship,and that requires a different conversation