Hot take: I haven't seen a compelling new phone feature from any manufacturer in as long as I can remember. I spend 99% of my tapping time sending texts, using a browser and taking pictures with the rear camera. Same as I did on my Droid X which was my first smart phone circa 2011.
Quality of the basics matters. Folks like to say they don’t need a fast processor, because all they do is browse the web. If you open the messages app and browser 50x per day (which seems like a conservative estimate) and load the maps app a few times a week, the speed differential between devices adds up. Personally, I find the annoyance factor more bothersome than the raw hours of wasted human lifetime. Side by sid…
The pixel 4 is older and much more of a budget device compared to the iphone 12, I am not sure why you are comparing the two.
That being said, my even older oneplus 6t takes around 200ms to open Firefox so I am not sure what is wrong with your pixel 4. Same on my partner's pixel 4a (which should be even slower).