Wilderness and parks are two very different things. Yellowstone is a fantastic park, which by all means is worth the trip to go see. But it's not wilderness. It is a designed and curated experience, by and for humans.
There's room enough for both man-made parks and wilderness areas, but to keep wilderness wild we need to stop making them human-accessible. I mean the whole point of wilderness is that it's not accessible, helpful, friendly, easy. The wild is harsh, dangerous, remote, unkempt, challenging, but also beautiful, tranquil, awe-inspiring, soul-filling.