Originally, RT was more or less a 'good faith' measurement of the general sentiment\quality of a film, but it is so easily manipulated it was inevitable that it would become meaningless.
While they definitely measure on different metrics, the goal of a critic is supposed to be to measure films worth watching (even if only for a subset of the total audience). When 95% of critics tell you to see a movie that only 10% of people enjoy, something's broken.
There are far more where the verified audience score is way higher and they tend to either be religious films or films with very low numbers of audience reviews (aka selection bias)