There are online articles about bots that snap up reservation dates as they become available. There are, also, many articles that deny their existence.
I'm very happy that you're so enamored with the existing system.
Perhaps you choose parks that others aren't interested in. Great.
As a test, here, just list a few major parks you've recently stayed in, after reserving sites on Reserve America. I'd like to try and reserve some sites to see if the process is as hassle free, now, as you wrote. My experience has been the opposite.
Here is an article that denies the existence of bots, while freely admitting that its company makes money by letting you know when sites are available:
Frustrated by bots scooping up all the campsites and selling them at a profit? You aren’t alone. That said, the situation isn’t quite that simple—a...
campnab.com
Here's another interesting article:
I'm glad you are so happy with the existing system. I think it stinks, and I'm not alone.