What should the conference acceptance rate be?
People who are dissatisfied with conference reviewing periodically call for conferences to change their acceptance rate.
People who have had papers rejected fulminate against the short-sightedness of the program committee: the committee applies an unreasonable standard that prevents innovative work from reaching an audience. But, I have heard the very same people also complain about bad papers that appeared: such papers degrade the conference and waste the time of the community (both at the conference and subsequently in reading and evaluating the proceedings).
These people want an exclusive and thus high-status venue, at which their own papers are uncritically accepted.
Those who propose a change to the rules of the game are wasting their breath with complaints about the unjustness of the universe. They would do better to: recognize that their opinion of their own papers is biased, deeply understand the referees' concerns (both explicit and implicit), and improve their research and its presentation.
My advice on writing a technical paper contains tips about benefiting from rejection.