We should assume sophisticated attackers, AI-enabled or otherwise, as our time with computers goes on, and no longer give leeway to organizations who are unable to secure their systems properly or keep customers safe in the event that they are breached. Decades of warnings from the infosec community have fallen upon the deaf ears of "it doesn't hurt so I'm not going to fix it" of those whose opinions have mattered in the places that count.
I remember once a decade or so ago talking to a team at defcon of _loose_ affiliation where one guy would look for the app exploit, another guy would figure out how to pivot out of the sandbox to the OS, and another guy would figure out how to get root, and once they all got their pieces figured out they'd just smash it (and variants) together for a campaign. I hadn't heard of them before meeting them, and haven't heard about them since since, and they put a face for me though on a silent coordinated adversary model that must be increasing in prevalence as more and more folks out there realize the value of computer knowledge and gain access to it through once means or another.
Open source tooling enables large-scale participation in security testing, and something about humans seems to generally result in a distribution where some nuts use their lighters to burn down forests but most use them to light their campfires. We urgently need to design systems that can survive in the era of advanced threats, at least to the point where the best adversaries can achieve is service disruption. I'd rather live in a world where we can all work towards a better future than one where we hope that limiting access will prevent catastrophe. Assuming such limits can even be maintained, and that allowing architects to pretend that fires can never happen in their buildings means that they don't have to obey fire codes or install alarms & marked exits.