Just because a song/item sold lots of copies doesn't mean it's good.
It just means people liked it. Which doesn't mean it's good.
Take the early Blues for example.
That stuff sold (and still does) lots of records.
Is it technically "Good" music?
No it isn't.
The early Blues was/is based on 3 chords...that's it.
Thousands of uneducated workers learned to play the Blues. no problem.
In essence.......Blues is atrociously easy/simple to play. (Over the year they've dolled up the blues in all sorts of ways to give it more appeal and technicality.......especially in the realms of jazz.....but at the end of the day it's a simple format and technically lacking........even though many buy it and consider it "good" music)
Had Mozart been living on the Delta at the time....he could have knocked off any blues tune you threw at him.
However........extremely few blues players of that time could play anything done by Mozart.
Because the works of Mozart are technically more difficult than banging off a blues song.
Technically, Mozart's work is better than simple blues.
In the same sense that a 10 x 20 ft shack built out of plywood is technically inferior to the Taj Mahal.
If you think technique is what makes music "good" then I think you have missed a great deal of what music is about.