I'm not rich and I fund the parks that I enter. Yes, this year I got an annual pass since I've gone to Yosemite numerous times. However, in past years, I have paid to enter Denali, Yosemite, Yellowstone and other parks.
To me, I kind of see it like places we often camp at in Alaska. There are improved campgrounds that have vault toilets, designated camping spaces, etc. Sure, we could just wander into the woods and camp but these campgrounds have amenities that are nice and take upkeep. I don't mind paying $20 a night or whatever to camp there. There is still plenty of public land available to everyone. It's just that there are so many people that want to see certain areas, they need to make improvements to the infrastructure to make it work.
Again, just speaking from recent experience, Yosemite is a joke on weekends. Thousands of people flock there. I don't hate that though as I do to. It's a beautiful place and how can you hate on people wanting to go to a park? The catch is that it is in one of the most populated states in the country and fairly near one of the biggest cities. If they didn't keep improving the infrastructure of the park it would be a disaster.
Sorry, but I'm more than happy to pay a little money to access a park so others can also have a better experience outdoors. Not everyone is a hard core backcountry hunter. fisherman, hiker, etc. But, I believe that the more people that are exposed to the outdoors and find value in it, the better our chances to keep it open and available, even if there are fees at some parks.
Oh, and yes, the parks are overcrowded. I "moved" to California for work over a year ago now and brought all my gear out thinking that I could go camp every weekend and enjoy some of the great areas. Sadly, I have yet to camp one night. There are just too many people and you have to book a space way too far in advance. As mentioned, I go to Yosemite often for photography. However, I don't go at normal times because it's just stupid busy. I drive in in the afternoon/evening when people are leaving and stay into the night. Obviously better for photography as opposed to hiking or other stuff though.