This is why I use external streamer boxes (Roku, Amazon FireTV, Android TV, Apple TV) that way if they just don't get updated, I just use a different one. Avoid the headache.
I think the Netflix app stopped working in my 65" Panasonic plasma 5 years ago or so. It was so slow when I bought it, it was almost unusable.
Newer models may be at the point where the hardware is powerful enough to have more lasting power, but historically, I have replaced my Roku or Fire (have tried different ones at different times) boxes between 2 and 3 years which has always resulted in an obvious and welcome increase in performance! My TV's on the other hand have recently been replaced after around 8-10 years - not because they had a problem, but because the prices have dropped so quickly over that time it just was too tempting to upscale the screen!
However, I would not want to suffer 8-10 year old streaming hardware (which did not work as well as Roku/Fire to start with)!
My point is that I do not believe the smart part of a smart TV has the same staying power as the TV. Perhaps the TV industry is hoping you will buy a new TV every time the streamer starts to fall short of new hardware. Unfortunately, I don't believe anyone sells a "dumb" TV anymore, so I would suggest simply adding an external streamer whenever you start to get impatient with TV's streamer (for me that has been as soon as I try it).
