The counterpoint to this is many studios are sequel factories, or producing games that are at least broadly in the same genre continuously, and each game starts

The counterpoint to this is many studios are sequel factories, or producing games that are at least broadly in the same genre continuously, and each game starts as a fork of the last, which is how you end up with things like the COD engine or Source 2 having a direct lineage to engines from 90s quake games. So "Assassins Creed: Odyssey" may not be an ongoing service, but "Assassins Creed" is, and tech carries forward from one to the next.