Or simply follow the on screen setup guide and connect it to the net in the case of a vizio. Then, it will auto update the firmware immediately without asking.
Not sure the point of your "Or". Whether it updates the firmware automatically without asking, or you have to select a prompt or menu option that tells the TV to go look for and install the update, those are still both "smart" functions. Even if you have to copy the firmware file to a USB thumb drive you downloaded with your computer, then connect the thumb drive to a port on the TV to install the firmware, that is still a smart feature.
Personally, IMO "smart" has become an over-used, and often misused "marketing" term. Traditionally, a "smart" device simply means it is an electronics device that has the ability to communicate with another electronics device. While typically that means the connection is via a network of some type, it does not have to be - as in the example of the thumb drive. It can also mean a simple wall clock that can sync itself via RF to the NIST time standard at Ft Collins is smart device.
Beyond that, it is all about the "features" and "services" that smart device provides.
I was very sceptical about Smart TVs at first
I was (and still am) very skeptical about smart TVs because many have integrated cameras and microphones and I do not trust they cannot magically

turn on by themselves - ether by a bad guy for nefarious deeds, or by the company wanting to collect "anonymized data" (spy?) on us for "legitimate"

advertising purposes.
And to R-T-B's point, I don't want any of my smart devices automatically updating themselves without asking. What if the update bricks my TV when I am not around? Will I even know why it suddenly does not work? And besides, I have always been of the mindset, "If it ain't broke, don't fix it!". So if working fine, I don't need no stinking firmware update.