Just to be clear, this applies to only the most popular parts of National Parks. Most National Parks don't require permits or they are easy to get. There are also tons of ways to hike that aren't National Parks. If you have the skills and gear, I recommend wilderness areas in National Forests.

This is like when that new gelato place opens up and has a 45 minute line for $15 ice cream, and the regular ice cream place is basically as good and has normal prices and no line.