If you hire someone and release them into the wild of your codebase, that's a failure on your part not theirs. New hires are an investment, they shouldn't be treated as an immediate need-based solution. My experience in two fields has shown me that new hires are a drain on resources for a fairly significant time period, regardless of their background. If you're not doing everything in your power to educate your new hires and get them up to speed, THAT'S your landmine. It's your job to get them to learn the fundamentals if they don't have it.
