For the most part phones don't have planned obsolescence, but rather technological obsolescence. Obviously there are cases like Apple deliberately slowing down old devices beyond the limitations of their hardware. But the Pixel 1 is what... 6 years old at this point? There are loads of reasons why your device feels more sluggish.

Hardware can fail or degrade over time, especially on something as delicate as a smartphone. Phones also use flash memory storage, which run better the less storage you use. (The same principle holds for SSDs used in desktop computers.) And you've probably had software updates or downloaded apps that recommend higher specs.

You can easily get five years out of any phone these days. I could've gone another two years on my Galaxy S10 if AT&T didn't have that ludicrous $800 trade-in offer earlier this year.

What I'd suggest is you backup any important files, and attempt a factory reset to see if your phone's performance improves. Your phone might have accumulated a lot of baggage over the years.