I have about a thousand times more confidence, that if I use my smart TV as a dumb screen connected to an Xbox one or PlayStation 4, that over a multi-year period of time, Microsoft and Sony will successfully keep their operating systems automatically patched, updated, and secure. As compared to any tv manufacturer.
I have seen people resort to things like installing pihole on their home LAN so that their smart tv will stop showing ads covering 1/3 of the screen whenever they use the menus. At least the advertisements that one will see on the home screen of an Xbox or Playstation are relatively small, unobtrusive, and can be ignored without bother.
In the future I think we will have problems with the fact that hdmi can also carry 100Mbps ethernet. Imagine if you plug your smart tv into some other device, intending just to send video to it, that gives it a dhcp lease and default route out to the internet. All in the name of consumer friendly "just plug it in and it works!" type functionality.