When I buy a computer monitor, I can pair it with any computer I want. I can upgrade the graphics card or processor independently of the monitor. I'm not locked in to a particular computer based on the features of the monitor I want. TVs should be the same. It could be as simple as a USB stick you plug in the back.
The implication here is that the connectivity tech goes obsolete quicker than screen tech. That has traditionally been true, but has it been over the last 5 years or so? We don't even have to get into the specific display technology. Just from a feature perspective, there has been a lot of innovation in screens including 4k, HDR, and high refresh rates.
Since the end of the digital-TV transition, the TV industry has been throwing a lot of stuff at the wall trying to find something that stuck. There's no clear "it becomes a paperweight" factor to make us all go out and replace newish sets right now. Remember the 3D TV trend? Or the year when everyone brought out curved sets, and then went back to flat? Smart TVs are another variation on that theme, with the added benefit for manufacturers that their lowest-bid tech and changing third-party service requirements will leave you with a set where half the hard-coded service buttons don't work and the other half are unusably slow to depress you into buying a new set in three years.
I expect the next real ecosystem change will be when ATSC 3.0 becomes a workable thing. Then you'll actually be able to offer 4K/HDR with an array of content without the caveat of "external game console/PC/streaming service required." I'd be a bit hesitant to get a new set until then just out of the risk you ended up with something not fully compliant (I'm thinking of those first-gen 4K LCDs that wouldn't accept a 60Hz input)
If you compare setups between a new TV with a few year old Roku, AppleTV, or whatever versus a few year old TV with a brand new streaming device, the setup with the new TV is likely going to be the superior option. In fact, Apple hasn't even released a new AppleTV since 2017. I have no idea if this will be a trend that continues, I just don't think "the streaming hardware becomes outdated quicker than the display hardware" is guaranteed to be true like we have assumed it was in the past.
TV display technology is likely to proceed in plateaus because they tie to agreed upon standards. By the mid 1990s we had the ability to make a 1600x1200 CRT monitor with a 85Hz refresh rate, but even a top-of-the-line TV wouldn't offer much more resolution or higher refresh than a 1965 model-- that's all you could get out of NTSC broadcasts. (Yeah. there were some progressive-scan input formats, but that's still only a token advance)
Introducing external sources (streaming, consoles, etc.) provides a bit of wiggle room to advance the resolution/colour/refresh rate bars, but that's still not going to change the installed base nearly as fast as if they said "here's a new standard format and every local broadcaster starts 8k broadcasts tomorrow."
In contrast, streaming products evolve in a continuous curve. Since there's very minimal, if any, platform standards, they can say "here's 24k resolution", or equally likely "here's a new codec/DRM format/API that old boxes don't support."
New streaming service comes out and there isn't an app for it on my device? Or security updates stop being pushed and now my device is part of a botnet? Now I care.
Don't you think it's more manipulative to build a one-sided argument into the question?
Not sure how that plays out in practice, but not a distinction without a difference.
Your argument is that this adds value to the chromecast dumb tv pair, despite being a fundamentally destructive operation.