The problem with this argument is that there isn't really a price difference between smart and dumb TVs anymore. While the failure point argument is valid, I wouldn't worry too much about it. If you never use the smart features then those parts are not going to have a high failure rate.
More importantly, if you do buy a smart TV and chose not to use its features you will want to make sure you spend some time with the remote in the store. You'll want to either check it out in a store that doesn't have wifi or that allows you to disable it on the TV to test it out. Find out how well it works as a simple screen. Is it quick to switch between inputs? Is the remote good enough or does it at least support using a Harmony replacement? Are interfaces slow because the software on it is too heavy?
Basically, I'm advocating that you just don't care what features the TV has that you don't use and instead find the cheapest set where the features you do want to use work well. If that set has smart features, don't use them and you probably won't have an issue.