I think the best way to describe the changes to maps is that the old version felt like you were looking at straight lines on a monotone background indicating where roads exist on a static plane whereas this version feels like you're looking at an actual map that someone has hand drawn by actually visiting every road, driving on them to scope out road markers, and measuring them with a laser to get accurate changes in width. There are no more road lines, they are now road drawings that give you a great sense of space, size, and movement.
The maps update is extremely impressive and without a doubt the best part of iOS 15 so far. It's a shame only a few places get it at the moment because it's awesome.