You very definitely can submit feedback on an Avis rental experience. We do it all the time on behalf of our customers. Direct link to the form here:

https://www.avis.com/en/customer-ser...ling-enquiries

There's also this one more specifically for feedback about a rental location, but the link above is the one we use (since most of the time we're dealing with billing complaints):

https://www.avis.com/en/customer-ser...tions-policies

All of those are accessed by going to Help > Customer Service > Comments & Feedback > choosing the feedback type from the "Change Topic" pop-up menu.