If you want to exclude certain products from being reviewed or exclude sending review requests to specific customers, go to the Exclusions tab under Store Settings.
You can get there a couple of ways.
The first way to get to the Exclusions tab is to find the link under the When to Send tab in your Automatic Review Request campaign.
The other place you can find it is under Store Settings.
There are multiple product or customer attributes that can be used for exclusions.
Here is a video on how to do a product exclusion in your store: