(Not that people won't figure out ways around them, but if Android were truly open to users you wouldn't need exploits to get around limitations...)
The blame should rest entirely with the carriers.
This isn't "Apple vs Android" this is "Apple vs Carriers".
That's an academic distinction, though, wouldn't you agree? Android as software is perhaps "truly open" but what about Android as a user experience?
Android, from the perspective of the vast majority of people who will interact with it, is what the carriers say it is.
The fact that there are multiple suppliers give the user choice. They can include how locked down a phone is in their criteria for making that choice, and buy one direct if they wish to have a phone that's not locked down by a middleman.
That phone is not publicly available unless you're a dev.
http://shop.vodafone.co.uk/shop/mobile-phone/google-nexus-on...
http://www.expansys.com/google-nexus-one-android-smartphone-...