brother no one not even scholars can claim to have perfect knowldge.So I do undertsnad the reason behind your saying this but if we abandon criticism of others than the principal of enjoining good and forbiding evil will become extinct. We have examples from salaf ( and many of them didnt even have formal religious training) criticized even each other if they thought it was appropriate. We should not get carried away by it either and condemn actions not individuals but simply being passive will allow whole society to degenrate.
Peace Das Reich
Allah (SWT) forbid I didn't claim that I sought perfect knowledge. Rather it was a need to observe my etiquettes with people. Not to talk on matters on which I have no authority. I can stop my son for example from littering in the streets, because the extent of my authority encompasses his actions, however, to criticise others on their practices based on semi-formed reasons from our own perspectives is not good criticism. We should leave some things to scholars as is their remit as authorities over us in knowledge. Afterall we quote them when they issue verdicts.
Simple well constructed and wise ways to criticise others can be done, however we should be more concerned with what we know to be true is actually true first. I don't mean this in the sense of absolute knowledge, but as fas as is possible for human capability to extend we should do this.