In pop the fan base is mostly bought through marketing, which is why social media is so important. Other genres may differ, obviously rock is traditionally gig/ tour based.
Pop artists are still found at 14-16 and work with management/ publishers before record labels release their music.
But yeh, you can make a brilliant quality EP for free these days, but I’m not sure the producers the record labels hire to mix/ remaster will see it that way. On that point, you wouldn’t believe the prices to have your music remixed by a known DJ.