That's not really it. Our company is small enough that I can talk one-on-one with the head of the tech department and I did give direct feedback about this person. That head of tech was responsible for the mishire, but also got rid of this person pretty quickly once all the feedback accumulated.
My company is service-based and just over 1000 people. Timesheets equal billable hours. It's occasionally very pressurized and we lose people pretty quickly when there's a lull in work, but it also means that useless people have absolutely nowhere to hide.
It sounds like your boss is making these decisions on his own without soliciting additional perspectives and feedback in advance as part of the hiring process. If so, that is a common pattern that, in my experience, leads exactly to these kinds of hires.
But with a fire-fast approach, it sounds like your company can move fast on hires and be ready to contain the damage.
My company is service-based and just over 1000 people. Timesheets equal billable hours. It's occasionally very pressurized and we lose people pretty quickly when there's a lull in work, but it also means that useless people have absolutely nowhere to hide.