For maps: either OsmAnd or Organic Maps. The first one is a beast but needs to be tamed, the latter one is more user friendly. They are both based on !openstreetmap@lemmy.ml
Well, best thing to counter that is to be the change you want to see. Start the community for the niche you miss the most/know the most about. Post something daily for two weeks + do a call for mods, and before you know you'll have at least some activity. I (helped) to bootstrap !openstreetmap@lemmy.ml this way, and the community has about 1 top level post per day on average now. Not a lot, but a good start.
Also have a look to https://mapcomplete.osm.be - this one works on mobile and desktop and has many thematic maps (e.g. one for shops, one for cycling stuff, one for toilets) and you can improve the data there as well + add images.
Well, I'm doing my best to get the !openstreetmap@lemmy.ml community started. Once there is enough activity here, the critical mass becomes self-reinforcing and it takes off.
And it's not as if all of Reddit will switch over right away - Twitter is still somewhat alive too; but Mastodon gained enough momentum now to actually matter and to be at a sustainable level.
Hi! Wrong sub? No worries, our subredditcommunity (!openstreetmap@lemmy.ml) is right here as well!
Did you also know that Apple Maps and Bing Maps use OSM data too in some areas, for some types of categories? Bing even has cloned an OSM-editing program.
Furthermore, you can use https://mapcomplete.osm.be to add shops or other POI. (Obligatory shill as I'm the main dev of that one ;) )
https://feddit.de/comment/2668592