Tap on a PDF and it will ask you if you want to open it in Dropbox, iBooks, or any other PDF reader you have on your device. I keep mine organized in the iBooks categories, myself, but other people use different apps.
So it's unacceptable that the iPad doesn't come preinstalled with all the things that you expect but it's fine that the Fire can be currently gimped by a lack of third party apps?
The point is that the stuff you were complaining about is available and out there for iOS. Whether it's pre-installed or third-party is pretty irrelevant.
iBooks wasn't around for the iPad 1, but things change.