I agree with your point that "each purchase vector should either be done right or not at all." In Pizza Pizza's case they should have stopped at an easy-to-use location finder with address and contact info and avoided the ordering bit altogether.
As someone who frequently uses the Pizza Pizza online ordering site, I couldn't disagree more. It has problems but it's way better than nothing or using the phone, which always becomes a clusterfuck because nobody can decide what they want until you're on the phone.