The mess they are leaving behind are outdated, crappy apps. They don't adapt to modern screen sizes, use memory efficiently, download efficiently (bitcode), etc.

Apple is continuously improving and modernizing it's platform. They should be banning hundreds of thousands of zombie apps that haven't been touched in many years because they are not valuable and misleading to customers. But they don't, they allow you to keep your apps available on the store no matter how old or how poorly written. Finally they have their first platform change that's going to break them, and they can automatically boot them. That's a very good thing.