What would be the downsides of simply buying a big computer monitor instead of a TV? It seems to me like an easy way to avoid all the crapware that comes with Smart TVs.
We did purchase a Roku stick a couple years ago, but they wanted credit card info during the set up, which I thought was BS for something that I just wanted to use for our existing streaming apps -- so we never used it.
The best way is to get a good smart tv (rtings.com) and do not connect it to your network. Use an Apple TV/Android TV/Fire TV device, it’s easier to avoid/disable crap.
You may say that that's the same as a Smart TV, and chromecasts come with their own crapware, but the big advantage is that they're separate devices. The Chromecast has no way to infect your monitor through HDMI.
If the Chromecast or whatever starts misbehaving, you throw it away and replace it with something else. You lost $50 instead of the $300+ that your Smart TV costs.
For lots of people, the builtin speakers and apps are fine. I also got the impression that TVs have gotten faster and UI are less sluggish. Why spend $50 for Chromecast when TV already has Android TV, and cost $200 cause going in spare room?
Don't have to use the smarts of smart TV. I never use the apps on my TV, it displays HDMI. I could stop applying updates or unplug the Ethernet and it wouldn't change.
The computer is a Raspberry Pi 4 running Kodi/LibreELEC. It works just dandy. I usually use CEC to control it, though sometimes I instead use a cheap Logitech K400 compact keyboard/trackpad combo. Both input methods are convenient (CEC even uses the regular TV remote), and both were plug-and-play.
It doesn't seem hard to use this computer from the couch at all, and it lets my dumb TV remain dumb while still accomplishing much of the functionality that I want from a video system that lives across the room from the sofa.
(And for everything else, there's Chromecast and friends.)