Yes, I've seen that happen with YouTube apps that are sometimes built into DVRs and the like. Google changes something, and old apps may break. If the device is no longer getting firmware updates, then you just can't use it for YouTube anymore. Have to go back to your trusty PC, tablet, or smart phone.
That doesn't surprise me, but it certainly surprised me that anyone would reach out and completely delete an app from a consumer device preemptively! Maybe they figured if it was going to break, it's better to delete it than to have folks calling Vizio complaining that their Amazon Prime app had quit working; but then, your Samsung tuner still works, and it's even older - so what could Amazon change that would break the Vizio app but not the Samsung one? (OTOH, it's possible that Amazon hasn't actually made the change yet, and when they do, your Samsung app will indeed break.)
It does make me wonder if Vizio was just trying to get you to replace an otherwise perfectly functional TV. I suppose that might have worked if you didn't own the Samsung tuner, but I certainly would have considered replacing the Vizio with a different brand! No sense rewarding such behavior.
BTW, I've also gotten an "update" for the Facebook app on an old BlackBerry, only to find that the "update" replaced the previous app (which still mostly worked) with a mere browser link to their web site. Took way too much of my time to find the old version of the app so I could download & reinstall it.
It's a bit scary to realize your apps can be yanked off your own devices at any time, pretty much at the whim of the manufacturer - or a hacker.