The pixel 2 is a straight up scam phone.
It always rushes about 2 months to get Oreo out before other phones have it so that it can have a temporary edge. If it took the additional 2 months it wouldnt have all the issues it has but it also wouldn't seem as impressive since all the devices will be a lot smoother, snappier and efficient once they're all on the same developmental cycle.
The pixel also doesn't have the hardware integration and optimization that galaxies have and that takes time. The audio, display, security, radio, etc all have hardware optimized functionality and capabilites that the pixel doesn't have.
It forgoes all that to have a bare framework that is much easier to have drop less frames and also much easier to patch.
There isn't any coverage of the hardware optimization that goes into galaxies so users are often surprised when they switch over to stock and find that so much of it is less refined and restrictive..
If all you do is use basic apps then you might not notice as much but you'll still miss out on all the audio video security radio and general customization refinements.
You also miss out on things like the pressure sensitive home button and app rescaler, auto hiding nav bar and lots of stuff like that. All that takes time.
Google can also get away with rushing out updates and then just patch up issues that users have later on