Paleontologists do not test dinosaur fossils for C-14 because they “assume” the age of fossils to be >65M years old. But if a really curious scientist were to test for C-14, I’m pretty sure they would find it. That might really shatter their faith in an old earth!
Each year, it’s fun to celebrate birthdays. If we’re not sure of someone’s age, we can always check their birth certificate. But can any reliable methods determine the age of an object without a historical record?