Android is open source. Android is not developed by an 'open community', if you will. It's a legitimate complaint, I think, but I wouldn't let the perfect be the enemy of the good. If someone wants to invest a lot of work and time, they can very much fork Android if they want, and develop it however they see fit.

Also, something else that isn't brought up a lot: Android has a fairly open architecture. Intents let you plug in various things in various places so that you can choose which app handles what.