OsmAnd is complete fail for the second part. Maps.Me has some reviews but it's meager compared to Google Maps ofc.
I have over a hundred reviews on Google maps that I wrote. I can grab them using Google Takeout and since they're my IP (I'm in Germany) I would happily import them as reviews for the resp. POIs in OsmAnd (or Maps.Me). I.e. use them to contribute to OSM.
But how? This should be dead simple.
If you want people to use OSM-based apps in place of Google/Apple maps you need to provide a way to access/add/edit (and better also import) POI reviews.
W/o them average users will not switch because offline navigation via OSM is simply not good enough a reason. Particuarly if you have commercial (but free) stuff like HERE WeGo which does offline navigation better than any OSM-based app I've seen.
Why does a review aggregator need a blockchain?
Also there is no way to import a review.json exported from Google Map via Takeout unless I'm blind.
FYI: You may want to check out Organic Maps, that is developed by the original Maps.me founders: https://organicmaps.app