It's worth your time to try, though. Google results are being offered for first-try for POI searches now; Map Maker often does work. And, while yes, your first few Map Maker changes will not be changed without review, once you've had a couple dozen accepted, they start to publish immediately — first address results, then POI results. So the more you try, the more effective you become.
Occasionally Map Maker will bug out completely (at least for me) when I'm trying to move an Address marker, but there is the alternative route of reporting bad data through Google Maps itself. Once when Map Maker bugged and didn't let me move an address, I (1) reported a bug with Map Maker, and (2) reported a map problem on Google Maps. I'm not sure which one triggered it, but I got an email a couple weeks later saying my change was made, and it was.
Yelp and Yellowpages aren't really worth your time; Bing isn't available anymore. I can't really judge with Foursquare, since I am a SuperUser over there, so I can move Foursquare markers no problem. But those tend to be accurate anyway.