I think it’s a little bit more complicated (and perhaps more “authentic” too) than you’re making it out to be. Labels definitely have strong influence in what gets played on the radio, but in your Cardi B example, Bodak Yellow was extremely popular on SoundCloud before it got any radio plays.

For your other questions, you can see in the credits of a song how many people are involved in radio hits. Labels invest money in creating hits so they can make money. The involvement and talent of artists varies from label to label and artist to artist but it’s generally not the organic process you seem to be hopeful about. At the end of the day, these artists have to perform not only in the studio but while touring, so they can’t be talentless hacks since some talent is required to be a profitable artist.