It really is a clapping issue. When I clap for you, it’s not worth much. I read and clap a lot. If you take my $5.00 (actually $4.16 — I pay $50 yearly, but we’ll keep it simple for the math) and divide it by 100 reads, you get .05 cents (a nickel.) If a new reader only claps for one story, yours, you get $5.00 (I imagine Medium takes a cut of that $5.00 but you get the idea.)
Getting featured by currators definitely gets you more views, but not necesarilly more claps. And even junky writing can get lots of claps if the writer is popular.
My biggest story, a fluke whose numbers are insanely beyond anything else I have written, has 6.4K views, 4.5k reads, and 117 claps. It has earned $100 total (since July 2018.)
So quality is only part of the factor. It’s a combination of quality, popularity, and who claps for you. How much time you spend on a story doesn’t even enter into the equation, other than, hopefully, contributing to the quality of the story.
I doubt many writers could make a living solely on the Medium Partner Program. Unless they live alone in a tent in the woods and have no bills.