There isn't one really. But you could pull up the ratings on google in a browser instead of having gmaps installed, which is better at least.

Something you learn quick about degoogling is that there's just some services that cannot ever match up with their product. Google Maps is one of those products.

You won't find apps that provide the same service as permitted by the entire Google ecosystem. That would mean that they are as intrusive as Google and you wouldn't be willing to use them. You either choose convenience and you can keep Google or renounce it a bit and use one app per function.

There is also https://mangrove.reviews/, with I believe is what map complete uses. It's open so hopefully mapping apps will start to really use them like Osmand or CoMaps

You can use TripAdvisor for the reviews

You won't find anything as robust as the database of reviews that Google maps has built up just due to their size and ubiquity, you'll have to see if you can find reviews on non-maps review sites like tripadvisor, yelp, OpenTable etc.

https://mapcomplete.org/ has reviews in some maps (such as the food map); but there are not a lot of reviews as of now. So, go out and review ;)

Apple Maps is starting to replace yelp ratings with their own. Usually some decent info in well-populated areas.