How do I address this lovingly and not come off as selfish?

Say repeatedly "Oh, I could never do that!"

You respectfully inform them that you feel inadequate, and you go with them to visit the MD about other options for their care. If they are in the hospital, you must make sure the discharge planner is not assuming you will be a caregiver. The discharge planner can arrange for a rehab facility for them. If you are badgered or made to feel guilty about this, you walk out. I repeat, you leave, excuse yourself, grab your coat and go.

I think it might help if we had more information. How is your health and what reasons do you why you cannot care for your disabled parent? What is your parent's disability and what limitations does this put on them? Are you an only child or are their other children in the family?

Hire a lawyer. That's it period.