If markets stop being efficient at price discovery, why wouldn't active managers and hedge funds exploit that inefficiency? In other words, why are active manag

If markets stop being efficient at price discovery, why wouldn't active managers and hedge funds exploit that inefficiency? In other words, why are active managers and their supporters arguing that they aren't good at their job? (The answer is that they would exploit the inefficiency and the market would maintain efficient price discovery, but they'll get more business by fear-mongering around index funds.)