I can sympathize with the fact that Smart TVs have a worse overall experience for you. The ads and crapware that you can't get rid of just mess up what was once a simple experience of turning on the TV. However I think smart TVs are a good idea because the way that people consume visual media is changing. More people are ditching cable and turning to services like Netflix. If HBO ever decouples itself from cable, I'd imagine this trend would increase more so. Why should I watch YouTube on my computer screen when I can watch it on a larger screen (and in a more comfortable room)?
I don't think the problem is with Smart TVs, I think it's just the current execution of the idea.
Currently, yes. I don't think that excludes the option of someone creating a smart TV that doesn't require an additional device to plug into it though.
Such a smart TV would have to be really well done in order to justify keeping the same privacy-invasive firmware around for the 5-10 year life of a TV.
I don't think the problem is with Smart TVs, I think it's just the current execution of the idea.