I don't know what motivates people to repeat this trope, when it is simply untrue. I think it stems from the fact that many people expect editing Wikipedia to be easier than it is. It is in fact quite hard. Some of the difficulty is essential (writing good, well-sourced expository prose is challenging) and some of it is inessential, the result of technical and social debt.
But most worthwhile things are difficult, and on balance, the rewards of editing Wikipedia are quite large in comparison to the effort required. You can go from a complete novice to a lasting (small) contribution to the project of civilization in an afternoon. You can't same the same for playing an instrument! And it can be hugely satisfying, really. Try it!