If it's okay to admit you don't know, then why demand that all believe? A demand for an unquestionable dogma is not scientific, nor is the use of shifting definitions in arguments. If you define evolution as "changes in animal species" then you'll find nobody, not even a 6k-year creationist, who'll disagree. Everyone agrees that species have changed over time. If you define evolution as it is forced upon us all as a new religion, then you run into more problems with belief. I disbelieve evolutionary theories for the same reason I disbelieve environmental alarmism: the command that I am required to believe. A billion PhDs do not grant the right to demand absolute belief from others.