It's a bad argument. It ignores the fact that humans progress by division of talent and labour. You wouldn't apply it to physicists, engineers, medical specialists, lawyers, politicians [1], financial experts, sports, or software developers.
So why is it fine to apply it to an art? The predictable outcome is that you'll get mediocre unsatisfying art that leaves everyone involved feeling like something vital is missing - which is more or less where we are now.
In fact it takes many more years of study and experience to become a competent, productive musician, artist, novelist, or other creative worker, than it does to become a software developer.
The arts are a profession, not a hobby. Just because most people can have a go doesn't mean it makes sense to run them on an amateur basis - any more than it does to run software development in the same way.
[1] The one category it probably should apply to.