There are two better options than deletion:
The first option (we think it's the best) is hiding that old question/field on the Enroll Form and the Customer App, so it's only visible to Admins.
Hide in Customer Portal - Hides the field in the Customer Portal so it is no longer visible to the customer.
Hide on Enroll Form - Hide the field on the Enroll Form so that new Enrollees/Customers will not see the field/question.
Within the field settings, scroll to the bottom and turn the appropriate toggle(s) on:
Export Customer Data
You can also download all the existing customers' data for historical purposes, including the old question/field, by exporting from the Enrollees table. Check out this support article to learn how to export data.