I don't doubt that ISO models are not optimal, but the annual cost of power outages to US consumers is above 100 billion dollars last time I looked already. Electric system reliability is a place where you have to be somewhat conservative as costs rise really non-linear with outage intensity. [1]

And ISOs/RTOs/TSOs operate in complex political environments and have to ensure reliability in adverserial markets. They are often constraint in what they can/can't do.

What I will say is that their modelling should absolutely be open and transparent, and typically it's not. That would make necessary discussions around modelling assumptions, potential improvements and political constraints much much easier and more fruitful.

[1] That said, my intuition is that current outages are probably not due to supply insufficiency, but due to transmission system failures.