This is the top tip to enjoy the parks. Don't go Memorial Day, Independence Day, or Labor Day, especially. The second tip, there a whole lot of parks besides Yosemite, Yellowstone, and the South rim of the Grand canyon. About 50% of the land area of the United States is for wildlife/scenic areas. Spread out.
For instance, Arches National Park has the most natural arches of any area. It is a beautiful, if somewhat crowded park. If you don't like the crowds, the second highest number of natural arches is about 100 miles east, down a 13 mile four wheel drive road, with a hike of maybe ten miles. You might see another person or two if you go there.
Visited the Grand canyon a few years ago about this time of year, it was awesome watching the snow squalls move across the openness of the canyon. Later we drove through Zion National Park, my favorite of all, should be on everyone’s bucket list.