To be fair, Swift have a bit strange generics implementation that forces programmer to jumps through hoops to achieve something quite common in similar programming languages. The whole standard library is peppered with AnyThis and AnyThat, the language doesn't have generators (yield) and I'm not sure they're possible with the current generics design and programmers needs to learn what is type erasure just because the core team decided that returning generic interface from a function is something nobody will want.

I like Swift a lot, for many reasons, but generics design isn't one of these reasons.