> I ask because I downloaded Maps.me the other day, after reading HN, and have found it to be missing most businesses that I've attempted to search for. In addition, there seems to be no obvious way to suggest missing destinations.

You might try looking at OsmAnd. It too uses OpenStreetMap data, but it does allow you to add some amount of missing data as well (see https://osmand.net/features?id=osm-editing-plugin).

This, of course, is part of the advantage of OpenStreetMap, you notice something missing, you add it, and now it is no longer missing.