The problem is that you cannot turn off much of the smart tv junk, including things like ads. Paired with features such as the tv refusing to work if you don't periodically give it a valid internet connection (for it to send its cached metrics and download new ads, of course), which is slowly but surely becoming more common, and you're only marginally better off than just using the smart tv features.
I've seen a few of them. They usually start with nudging for the first few weeks ("hey, you should really plug me in and get an OS update!") before eventually refusing to work at all.
