There is no well-known website where people can get reviews and user opinions on Crypto Exchanges, ProExchangers is a platform where people can go to get user opinions and give their opinions on Crypto Exchanges.
This description isn't enough reliable. Mainly because there are good platforms that provide this kind of services. I can advice you to take a look at :
-Revain platform here :
https://revain.org/ which is a great source of reviews about exchanges and other crypto entities. I use it frequently by adding feedbacks about my experiences with different platforms.
-BestChange (link in my signature) which becomes a well known platform rating good exchanges. And i think it is not that easy to compete with it as it's a public platform which requires no registration to be used.