Maybe it's not just the concept of VIVA that's the problem, but also maybe it was just too soon. If YRT developed a more comprehensive system like Mississauga and Brampton did (before Zum) to prepare for VIVA, then maybe it wouldn't be experiencing these problems. MiExpress and Zum were rolled out much later than VIVA, and more gradually, at lower cost, reinforcing the rest of the network instead of cannibalizing it. I think that's the approach YRT should have taken. YRT was just not ready for 5 new frequent all-day express bus routes all at once. And let's not forget that VIVA itself has seen massive service cuts.
We can talk about facilitating transit-oriented development, but people in York Region are literally becoming less transit-oriented (ridership is falling). There is some effort at intensification, but I don't see how that's different from what Mississauga has been doing on a much larger scale without a VIVA-style system. Both Mississauga and Brampton have seen better ridership and service growth than York Region since 2005 (the introduction of VIVA). I think that is ultimately what shapes development.