For me, iCloud has significantly improved over the years. It is reliable.
However, I am always perplexed by the slowness of the iTunes Store the App Store and related services. Perhaps it's because I live in the UK, but these services have been consistently slow and flaky for as long as they've existed. In comparison, Amazon's app has been much faster and slicker for the same period of time. I can only assume it's because of Amazon's superior backend servers, which are better optimised for speed and efficiency.
I think Apple should admit defeat and simply use Amazon's services wholesale, as they are clearly superior. It's now been over ten years of Amazon's dominance in this field. Much of the same also applies to Google services, which are often superior.
Funny how after all these years, the leopard's spots haven't changed. Apple still suck at services and Google still suck at hardware. If only Google hadn't backstabbed Apple back in 2007, we could have seen an amazing partnership between them amalgamating the best of both: Apple's superior hardware with Google's superior services. Ah, well.