It seems silly that "simple" things like custom ringtones and copy+paste are missing, but you gotta remember, the entire thing was built from scratch in a short amount of time.
All of those "simple" things still need to be fully implemented and tested. And sometimes they're not as simple as they seem.
-copy+paste introduces potential security issues since everything is sandboxed
-custom ringtones have all the minutiae of where can you install them from, a service to host them on zune, format support, etc.
Building it from scratch, all those things take time, and something's gotta give. A couple weeks here or there add up when it's a bunch of smaller things.
When it comes down to it, it's a hell of a lot easier to add in features like copy+paste and custom ringtones later on, than it would be to, say, add customizable hubs later on. Or support for plugins like Youtube. Or Facebook integration.
It's not a defense or a justfication - if you want those features, depend on those features, by all means don't get the phone! But at least Microsoft's explanations make sense here.