Think of it like high school. Level 1 is like being a freshman. Everyone has roughly the same basic elementary knowledge. Some might be better at some things than others, but they are still babies in even those areas, unless they're prodigies.
Level 4 is like maybe Junior. You have, by this point, started to really veer towards one path or another, but you still need a lot of refinement.
Then Level 5 is like you are on your last year of high school. Now you are really choosing your major and charging towards your career. After that, you are like in college until maybe level 8. Now you are a true pro, and you are significantly better at your craft than everyone else.
But that's not how D&D portrays experience levels, is it?
Level 1 characters are already young professionals with training even though inexperienced. A proper comparison would be graduates. In 5e a level 1 bus driver with no medical training can succeed in surgery where a trained surgeon can lose a patient. We even have an actual scene for that on the nautiloid. =)
