Implementation and adoption are part of the complexity of a solution, in my book at least. I assume those who do not consider implementation and adoption part of the complexity have either come up with genuinely simple solutions to problems or never had to complete those portions of the task when they were not simple.

Implementation is one paragraph of SQL or statistical code, given access to the data set and a few minutes to execute.

This change in how revenue per song is calculated is truly simple.

The only hard part is convincing people it's better.

Adoption has nothing at all to do with complexity. Be careful you're not moving the goalposts.

Bill gates giving me a billion dollars to screw around with is extremely simple, and also will never be adopted.

Adoption is directly effected by the implementation and design you choose. If your app is nothing more than a table and some aggregate statistics, because you just made the simple implementation with absolutely no design, then good luck getting musicians especially older ones who probably still rely on paper copies of their monthly records being gasp mailed to them to adopt the app.

It is not moving goal posts its considering whether the 'solution' will actually work given circumstances outside the technical feasibility.

The old method mailed them revenue taken in per song. The new method will do the same. You mail them the same sheet as before, but it's probably more fair.

The old method mailed them how many times a song was played and total revenue for that song. Therefore it was easy to see the rates. With what you are describing they would only see average rate if you mail them the same sheet. It is not the same.