The problem with this argument IMHO is that if it were true, one would in fact be able to just bang out hits by developing such mastery. But music hits get popular primarily on the basis of luck, survivor bias, branding, etc, not strictly based on artists' composition skills. There are plenty of very talented one-hit wonders, and even criticisms that popular music is "manufactured" (implying that it is relatively easy to just follow some vague formula of 4/4, II-V-I chord progressions and lyrics about love and end up with something that resembles a hit).
Isn't this exactly what Max Martin has been doing for last 20 years?
But given how many musicians and producers exist and how utterly small is the percentage of people who are comparable to Max Martin, I think it's reasonable to speculate that his success might be partially/majorly attributed to factors of luck/survivorship bias/branding/popular-music-as-a-mass-produced-product I mentioned.
I see arguments like this a lot and it think it conflates two very different kinds of "technical difficulty"—design difficulty and execution difficulty.
Given the sheet music, any guitarist can play 7 Nation Army in a few minutes. It is not physically difficult to play. Also, it's not hard to come up with a completely original melody or artistic work. Just throw a couple of random unrelated things together.
But it is extraordinarily difficult to have such a mastery of composition and understanding of what music is already familiar to people to be able to find a melody that is both original and enjoyable to a wide variety of people. The level of cultural, musical, and historical knowledge required to do that is extremely difficult and rare.
It's like taking your boat to the world's most popular fishing hole and knowing where everyone else fishes so well that you can still manage to stake out an unvisited spot that hasn't been fished out and reel in a giant.