In short:

1. Increased graphical fidelity means that you need more people to create the same scene. By way of a source of his, he gives the example of a scene from Final Fantasy IV and how many people with specialized roles it would take to create the same scene in modern graphics compared to back in the 90s.
2. Larger team sizes means communication takes longer. For everything. No longer just one studio but multiple studios in multiple locations and time zones working on the same game.
3. Scopes are bigger. Players are expecting more, whether that’s more hours of content for your dollar or more reflective puddles. May become a vicious cycle as this means you now need to make your game appeal to more groups of people in order to justify your larger costs from this and other areas.
4. Technical challenges; changing game engines or platforms over time. If you need to upgrade your engine so that it supports outputting to a console that came out while you were developing the current game, it affects more than just the version that ships on that new platform. Or any other way a game might need to upgrade to support some ambitious new thing the game is trying to do.
5. Covid happened in the not-too-distant past, and everyone had to change how they work on a dime.
6. Mismanagement, though a bit too umbrella of a term. He feels the number 1 reason is managers deciding every game needs to be a live service, not playing to the developers’ strengths. He also cites shifting timelines by 6 months at a time instead of actually evaluating how much time the game really needs; upper execs not being decisive about a direction for a studio while the studio is strung along for months before minds are changed; short-sighted layoffs between projects breaking up team chemistry; etc.