You missed the point. iTunes is a old product holding together well.
* No doubt if iTunes was designed today it would be completely different. But as a legacy product it has to satisfy legacy users that are familiar with the UI, and legacy products (this iTunes still supports 10 year old iPods and older?!!)
* Say iTunes failed today. No doubt the writer would say it deserved it, and the product was a failure from the beginning. But I want to emphasise that iTunes has existed for several years now and has given many hours of pleasure for many millions of users. it works well and is a success.
You are naive if you think iTunes one day will work well. It won't get better. What is going to happen with it? It is obvious. You don't have to go past Microsoft with Internet Explorer. They kept that product going for years and it was a great success. However eventually the tech aged and they replaced it with a new product, Microsoft Edge. The same will happen with iTunes.