It sounds like the main problem is your focus on hiring senior people. Maybe you should go with Reid Hoffman's advice and try a junior person making a mid-care

It sounds like the main problem is your focus on hiring senior people. Maybe you should go with Reid Hoffman's advice and try a junior person making a mid-career change. There will be more risk, but you stand to gain top-notch workers who the rest of the market ignore due to conservatism and credentialism.