The criticism in this case is completely bonkers. They reuse assets from previous games, even adding more while developing.

This only means that they have an ever increasing repertoire of assets from all their games, from which the designers can freely choose. And then of course they match the asset to the new game (adding a grunge pass for a zombie game is the example given)
This is the optimal way of doing it. They save time and money and have lots of different assets to choose from.