I spent a few hours last night adding buildings and restaurants and removing incorrect items. It was actually kind of fun and therapeutic and I plan to do more of it tonight.

Same here. I actually use OSM editing as others would use drawing. I even edit on OSM while engaging with people, just as others would sketch in their drawing book.

My girlfriend thinks it’s dumb and I’m wasting my time because Google maps and Apple maps and Bing maps exists

In case you or she is into hiking: Komoot is literally using OSM data. Paths for hiking and cycling outside the city are almost nonexistent on the big commercial services. When I'm going for a walk and I find a trashcan, I add it to OSM while I'm walking. My thinking is that people might be less likely to throw trash in the woods when they know that a trashcan is just around the corner.

Apologies, I just realized this question is not Linux specific.

"Has anyone used or contributed to OpenStreetMap, the data source of popular Linux apps Gnome Maps and KDE Marble?"

FTFY