I've worked with plenty of tech and related people who didn't understand basic technologies we expect in a given field.

I tend to reserve judgement until their effort can be judged. If he or she is slow but learning and improving, I'd accept (and probably raise with a manager) that the hiring process is flawed and try to help him/her.

If its just utter idiocy, I'm less forgiving.

I literally had a business analyst come to me - the new guy at the time - on her last day after several years of working in the org and ask me what her email address is.

Or the BA who insisted she didnt need to write a clear and specific spec for a feature, because she could just open up dreamweaver and put some buttons on a page.

Those sorts of people I have zero fucking time for, and will drink merrily when they quit/are fired.