There is nothing magical about the iPhone especially not on the hardware side.
I don't know how but if you look at input response time charts, especially in the early days, the iPhone is among the best, if not the best by a large margin. Less abstraction layers? Better tuned OS? More attention given to latency? More trickery? Apple's level of integration and closed ecosystem certainly helps here, and I can easily imagine Steve Jobs pissing off every single employee that wasn't fired for the smallest hiccup. I am far from an Apple fan and I don't own any of their stuff but I have to admit that on some points, they are really good. And as a developer, I have a lot of respect for those who care about performance.
Your OnePlus 7 Pro is a beast. It is fast and smooth because it has quasi-desktop class hardware inside. That's the "solution" I was referring to.
To be fair, Android did work on smoothness. It was called "project butter". But IMHO, they still didn't manage to match Apple on equivalent hardware. I don't know about the situation right now but I hope everything is smooth considering the ridiculously powerful hardware they put in modern flagships.
