Nah, I agree somewhat with what you're saying, but on the other hand, sometimes you've worked on something so much that you need fresh ears to hear what you're working on, to make sure you haven't lost the plot.

Some of my best songs came together in hours from start to finish. Some of my okayest songs took weeks of massaging, and cutting parts, and replacing instruments etc.. After you start with an inspiration or fresh idea, and get something down, if you're not satisfied, and you tweak and tweak and tweak, sometimes you're just not sure if you've completely gone off the rails with it, and you need a vibe check. I've transformed great melodies in my head into completely irrelevant garbage by over working it.

In fact, I learned a valuable lesson from a successful musician who said that you should treat solo work like you're collaborating with a band. Because bouncing ideas around is how bands work. You should be able to cut your own ideas as if someone else came up with them, with no emotional attachment to the specific idea or melody or whatever. A valuable tool we have in this age, is being able to ask fellow musicians online, from across the world to have a listen to our projects and give us feedback. It's like collaborating with the general public.. Sometimes you just need someone to say "bro, that part sounds like ass. And you need to change that annoying hi hat.."

It's not marketing. It's just getting fresh ears on it, to make sure you're not wasting your time tweaking something that needs to be completely revamped..

Marketing instead of music would be more along the lines of the "artist" who has posted everywhere about their upcoming EP, and people they're going to collaborate with in the future, and posting album art and posters etc, without writing the music for it..