The person who cannot contribute equally may still want a useful way to participate.

Excusing someone from helping is not always a kindness. A person whose money, energy or mobility limits what they can give often ends up placed outside the effort entirely, and that placement says something about their standing that nobody meant to say. Contribution can be resized rather than removed.

Instead of telling someone not to worry about it, offer a specific job that fits what they have: the phone calls, the list, the hour on Thursday. Let them decline it themselves rather than deciding for them.