I most certainly asked it in the OP: How do we decide what is reliable ancient history? Many accept something as historical without asking further questions. That's not how historians work, whether investigating Benjamin Franklin, Captain James Cook, what happened in World War I, or Jesus of Nazareth.
It is true however that some accept things as historical without asking further questions (agree this is sad). I also see a second problem...SOME people refuse to apply actual critical thinking and believe others who make up ever newer criticisms (not the same)..