I can appreciate why people don't want slots however you have to look at it from the organizers point of view.
Having slot times means that you get a steady flow of arrivals.
This is a big safety consideration, if everybody arrives at once things rapidly turn into a shambles, including the marshaling and ground handling.
Some locations have limited parking so have to limit numbers for that reason.
Try running your own event! It's Bl**dy hard work but well worth it. Just think if people didn't put on events you'd have to stay at home and moan about the food and the toilets there.
