My in-laws have a fairly high end Sony smart TV (Android TV based) from only 3 or 4 years ago and it's the worst POS I've ever encountered. It was always a bit sluggish (flipping through menus, changing channels, etc) but recently it has slowed to an absolute crawl. Any type of App or even bringing up the menu takes like 2 minutes, and turning on the TV takes like 5 minutes. Once it's booted up, at least flipping through the OTA channels "only" takes about 2 or 3 seconds, so it's somewhat usable.
My initial instinct is that some sort of hardware is failing (storage, maybe?) but it was quite slow to begin with, so it's plausible a software update is the cause.
When I was a kid my grandparents had an old style TV with vacuum tubes. It also required several minutes to “heat up” before the picture appeared. I guess we’ve come a full circle.
Adding an anecdata to the pile - my parents have a Sony Smart TV and yeah, it's a POS. Trying to watch some YouTube videos at Christmas and it would frequently crash with "This page requires too much memory" errors.
At least on my LG TV, basic non-"smart" controls are available directly via both RS-232[1] and IR remote without recourse to menus.
The IR remote, in particular, might be a solution for your in-laws' TV, as LG-compatible IR remotes are "plug-and-play" and available for less than $10 (avoid "service" remotes for this application, as they include a button that makes it easy to accidentally factory reset the TV, which is both annoying and, in the case of OLED TVs, maybe even potentially harmful[2].
RS-232 is particularly nice for tinkering with one's own TV, as it allows you to disable the OSD entirely, completely neutering all smart TV functions and pop-ups until the TV is turned off (or OSD is re-enabled via RS-232), and also includes video and audio controls not available on any of the IR remotes I've seen (brightness, contrast, bass, treble, etc.).
Along with a 4-port IR-controllable USB switch[3] and an audio interface with a TOSLINK input[4], I use the RS-232 functionality as a basis for my desktop "KVM", with inputs, brightness, power, and volume controlled with an Apple Siri remote paired to a Mac.
The only times I touch the menus are rare cases where I actually want to use the built-in smart TV apps (viz., for 4K video from services that don't support it on Mac or PC).
[2] Source: unconfirmed Internet claims that the button resets a panel refresh timer that may lead to burn-in and warranty invalidation, which seems crazy for something that could be triggered without confirmation by a simple IR command one might accidentally mis-program into a universal remote by mistyping a single number.
Which is awesome and highly recommended, but for the present application any USB audio interface with low-latency monitoring and TOSLINK should work as well (and if you don't care about mixing the currently active HDMI audio source with other audio like I do, the volume on the TV's built-in speakers and non-digital audio outputs is controllable via RS-232).
My initial instinct is that some sort of hardware is failing (storage, maybe?) but it was quite slow to begin with, so it's plausible a software update is the cause.