MapQuest uses OpenStreetMap data, or at least shows me stuff I added to OSM in my vicinity. On their mobile website they seem to be missing attribution, though!

Yes. but remember that openstreetmap is the database. Its third party applications which will expose and build upon it, e.g. including searches in DDG and Facebook and Apple. The project website is not a one stop shop to compete against gmaps.

Certain apps do, I recommend https://organicmaps.app/, which can also work completely offline.

Of course the data can only be shown if someone adds it; with OMaps you can contribute for example `opening_hours` and the pub which is non-existent in OpenStreetMap ;)

I wish those didn’t exist. They’re wrong a lot. And people think they’re some official source of business hours even going as far as saying “on the website it says the hours are”.