Their tech debt for the most part isn’t going to be because of the engine. Certainly some of it is. But starting back over and reimagining most of the code base affords them the time and ability to fix problems that make features problematic. As the spiffing Brit likes to point out every one of their titles is absolutely riddled with game breaking bugs. Doing an engine change has the kind of depth required to let them head those kind of problems off before they happen.

Of course with an entire staff of short timers they’ll quickly just a mess new tech debt as they misgauge things.