Just tried it on mobile and that is nice and easy, especially if you want to add a business. Not sure how you add a bench that way as I couldn't see the option, but I might be looking in the wrong place.
You're right though, installing another app store is a non starter.
On desktop, right click on the map and choose "Add a missing place." On mobile, long-press to drop a pin, then scroll down to "Add a missing place."
Does OSM require installing a parallel app store to add a park bench? Sounds like a UX-killer :/