Awesome game! I assume I 'completed' it given that there're no upgrades left on the map.
I do think the prestige mechanic could be improved. Once you reach good trophy production, the main way to progress is to prestige the same car over and over again very rapidly, which gets kind of tedious. I've practiced it so much that I can prestige a car in 8 seconds by now. The game also goes very fast once you start prestiging, going to the end of the game rapidly