if you're thinking purely about game loops and game mechanics, yes a lot has been done before and used over and over again. but that's by no means all the programming going on.

just look at how much people complained about poorly optimized games in the past decade. the most impressive game dev feats in terms of programming were not the game mechanics, it was getting their game to run as well as it did on (very) limited hardware resources, a problem we are hitting again now. and it is very obvious looking at modern games that this problem is nowhere near solved, and in fact very hard.