You can easily unenroll a contact from Engage if you do not want them to receive emails.
Go to the Engage tab and click the Enrolled filter to see all contacts currently enrolled in Engage.
Search for the contact you want to unenroll in the search bar.
Click the three dots on the right side of the contact and then click Unenroll.
You can also unenroll from the contact page:
Go to the Contacts tab and search for the contact you want to unenroll.
Select the box next to the contact(s) and click Unenroll Engage on the top right.
You can also click into the contact to open the contact page. Click the three dots next to the contact details on the left. Then click Unenroll Engage.