Look, the province put out a huge list of projects deemed to be of REGIONAL importance and this included Transit City because Transit City was Toronto's priority. Now that priority has become even more narrow.
Despite their desire for the subway it's important to remember YR was not expecting that announcement. They were on the brink of moving forward with BRT for Yonge Street - literally, approving expropriations that week. Since then, they've done extensive consultation and completed EAs so I utterly fail to see how, at any point, they can be faulted. The NERVE of these suburbs trying to actually build transit-oriented development with, like, transit!
It's people on this board who turn it into a 416-905 thing. It's pretty clear, I think, that the whole reason Mlinx exists is because TTC and other transit bodies could not be trusted to coordinate on creating a regional system. As we speak, Mlinx is evaluating the Yonge extension in the context of other needs (including DRL) and will eventually "rule" on what should be built first, when the money's available. Then the province can abide by or ignore that recommendation.
I 100% understand the need for DRL but it's always been the city that failed to prioritize it and no one is going to land a definitive argument for why one project has to go before the other; they're both needed and funding is scarce. But York Region has done everything anyone has asked when it comes to trying to push intensification and cutting off their balls at Steeles Avenue (or Finch, for that matter) is self-defeating for their entire GTA, IMHO.
By contrast, the DRL barely even exists outside of this board. You never see it mentioned in ANY of the articles about how Ford re-jigged Transit City, for example, because even Mr. Subway doesn't have it in his Top 5 priorities (maybe Top 10?). In that context, why should Metrolinx or York Region be forced to defend it?