I adore Marty Cagan and his sassy, tell-it-like-it-is-because-I'm-privileged style. I hear he's not nice, but I don't really care. I love the Nirvana Product Model and would argue that it's what a lot of agilists aspire to.
Having attempted the shift to product teams on a few occasions, my thoughts are this:
If the company isn't ready to make the shifts in power, structure, and intent, trying to move to a product model is going to hurt.
Applying the product model requires killing some sacred cows. Most organizational systems have active defenses, so it takes strong leadership *across the layers of leadership* to make it happen in a company that has been doing something else for decades.
When we're talking about "agile being dead" (for the umpteenth time), we're essentially saying "the attempt(s) at agility that we tried in my context didn't work." And then because we're human, we generalize to all the things. This is throwing the baby out with the bathwater.
I would really enjoy hearing about what newer, better, harder, faster, stronger methods you're exploring and what you're figuring out.