Sounds like organizational failures all over the place, not the fault of contractors.

You're not wrong. This falls on the managers heads as much as it falls anywhere.

I'm not blaming contractors for being contractors. A lot of these folks are straight out of college and new to their respective fields. It isn't there fault that Deloitte or Accenture or whomever spent six weeks teaching them to make power point presentations rather than giving them a proper six month seasoning in proper standard business practices. Even less so when the folks running my own company never bothered to learn how to do things properly themselves and don't appear to know who to ask.

But the consequences of the practice of hiring a flood of pricey contractors to do implementation and then leaving the maintenance to a bare-bones staff is misery for everyone involved.

So management and current team let in garbage code

Management doesn't know shit for shit about coding. The current team doesn't get to vet and approve the code that's released (as if we've got the time given our existing maintenance roles). They only get to handle the final product that's delivered. That is a central problem with the business model. Trust is invested in contractors that isn't earned or deserved. Meanwhile, the expectations of functionality are transferred to the skeleton crew staff once they leave.

I don’t think adding another employee to an environment with broken communication and no code reviews will improve anything.

I think you can't get to an environment of effective communication and consistent code dev/review standards if half your workforce evaporates at the end of the contract period. As it stands, we've got managers stacked six roles high while the actual applications have maybe 1-1.5 employees assigned to each. So who knows the systems well enough to review the other guy's code?

Having a mentor-mentee relationship on each app would be much preferable to a contractor-for-a-year/single-support-specialist-for-a-lifetime situation we're dealing with now.