Literary criticism today works the same way that medical research would if every researcher arrived with an entirely different approach to medicine. Like one guy's homeopathy, another one is faith healing, another one is ancient Vedic, etc. And they're all talking and using the same tool set, but their ways of evaluating what they see are so different that there's effectively no dialogue. No one can assign legitimacy to anything because any pretension to decision making has been given up.
Keep in mind that I once did lit crit. I guess I didn't come out of the right school, because I couldn't see any point to it. That didn't stop me from picking up multiple degrees in it.