I don't know what the solution is. The reality is things are totally different today from when the National Parks were created. People now have the ability to easily get to them and experience them. That ease creates a numbers problem.
Yes, the parks are supported by our tax dollars. Another reality is the money the parks are getting from our tax dollars is not enough to maintain the parks. There is a serious backlog of maintenance issues.
Here in SC the State Parks have to be able to sustain themselves. This has actually improved the parks. Yes you pay to get into the bigger and popular parks. Those fees also help keep the crime down.
Again, don't know the solution but something has to be done. Will be camping for a week in May near the GSMNP before school is out, so hopefully not too bad. Went to Grand Canyon last year 2 weeks after Easter hoping to miss Spring Break and had no crowd issues. I am sure COVID helped the crowd issues there last year.