One thing you're forgetting is that smart TVs are much cheaper because the cost is subsidized by the apps, software, and ads. This is why many of these "dumb TVs" aren't hundreds of dollars cheaper than their smart cousins.
In my opinion it doesn't matter if outdated software is "baked into your hardware forever" because all I have to do is disable the Internet settings, and plug in a roku/chromecast just like you would on your dumb TV. Difference is my subsidized TV cost way less. In terms of value over time (which is what I assume you meant by calling it an investment) a smart TV makes way more sense even if you don't use the smart features.
In my opinion it doesn't matter if outdated software is "baked into your hardware forever" because all I have to do is disable the Internet settings, and plug in a roku/chromecast just like you would on your dumb TV. Difference is my subsidized TV cost way less. In terms of value over time (which is what I assume you meant by calling it an investment) a smart TV makes way more sense even if you don't use the smart features.