I also have an iPhone 8, this is an Ok phone but is a worse experience than the 4 year old Android phone. Despite the cost being much higher, the screen is worse quality, for instance.

My partner has a 6 and it is remarkably slower than both. To the point where you sometimes just want to give up on whatever you were trying to do while waiting for a map or Spotify to load.

Maybe your experience is different to ours, but I'm only reporting what I see from using all 3.

You're lying. Installing a custom third-party Android ROM is way more than a 10 minute process, your OnePlus X is barely more than 3 years old, and there's a huge difference between a random OS image you downloaded from a forum online and manufacturer-supported OS updates for a 5 year old phone.

iPhone 8 vs Nexus 6 from 2014, back when Google marketed that series as reasonable Dev devices, not necessarily flagships.

326 ppi vs 493 ppi

750 x 1334 pixels vs 1440 x 2560 pixels

IPS LCD vs AMOLED

Somewhere there is a tongue in cheek meme comparing a sister phone, the Nexus 4, from 2012 against a 2016(?) iPhone and it's quite interesting how many features the Android phones had and were mildly credited for that when copied to iPhone were /world changers!!1/

Granted, Android phone manufacturers have wised up and besides things like the Nokia 6.1 you can't really get a good mid-range Android phone any more... it's mostly clustered around either the humble Moto E or the Note 9 price points.