Try imagining a literal five-year old in a grown-up body. That's what this person is like when it comes to anything that does not have immediate (< 5 minutes) consequences.

I say this with love, to be clear. They are the most wonderful person. But I could not live with them without support.

Any system that accommodate this type of problem needs an external support structure to offload the burden on many other people. In our society, we call it mental healthcare, and we use diagnoses to help triage.