In my last response against an AI assisted attacker who knew what they were doing, it was like playing WarGames - by the time I identified a compromised ID, there was nothing left but a smoldering hole- everything that identity had access to had been exploited and lateralled in moments. Effectively instantly.
Even a large team of seasoned red teamers can't enumerate access paths and pivot that fast. Even with scripts (unless the scripts are basically doing what the LLM does)