The “Do not contact” field is a hard opt-out of all marketing activities and - in my opinion - should not be used to mark contacts as inactive. If one day you decide to run a reactivation campaign these contacts will be excluded.
There is a - again in my opinion - better approach for this:
Use the “Data Last Active” contact field to create a list with inactive contacts
Use a campaign to tag the inactive contacts (or remove the tag if applicable)
The Do Not Contact field is intended for GDPR/privacy purposes: it is a field that is flagged when the contact doesn’t want to be contacted by you anymore.