No, the rest of the park is NOT like the lines. The lines are in a contained space and that amplifies everything. But, to somewhat answer your question, my son does put on ear defenders when walking around the parks when there is a live performance or parade happening, or anything else that is too loud. He wears a baseball cap and sunglasses and pulls the hat WAY down to limit visual input, and generally walks very quickly from place to place. He actually doesn't ever get bumped while just walking around. He is very good at weaving through crowds and avoiding contact. So good that we dress him in neon colors because it's easier to keep tabs on him as he walks 20 feet ahead of us most of the time. And to answer your last point, if he crowds someone and they tell him to back off? He will likely not react at all, and will completely ignore the person because he's autistic and 1. He won't realize he is being spoken to directly unless you address him by name first 2. People with autism generally don't respond to social interactions the same way NT people do and 3. He won't respond to a comment like "back off" by actually moving away because it's not a phrase he would understand. He would respond to "you're standing too close to me, can you please move backwards a few steps." You have to be really clear and direct with him. As it is, WE are always the one either telling him to move away from the person in front of him, or physically have to pull him back, or physically have to stand in front of him and create a buffer zone. And honestly, it gets very tiring. We don't want others to feel uncomfortable and feel like they need to confront him in a line. He is 12, but behaves more like a 4-5 year old, he is very aloof, and he is also VERY sensitive and cries easily of people are mean to him or generally harsh towards him. He is a very sweet boy who is very confused about the world much of the time. He absolutely LOVES Disney parks though and they are one of the few places we can successfully go as a family and consistently have a good time. Most typical leisure places people go with their kids have been massive failures for us (sports games, bowling alleys, minigolf, hiking, the beach, etc).
Your point that it "worries you that parents expect other people to adjust to their child's behaviors" is PRECISELY the reason for the DAS. We do NOT expect anyone to adjust to our child's issues. That's the whole point. The DAS allows us to AVOID that scenario by giving us an alternate waiting location so that these line behaviors won't affect others.
I don't expect the world to bend to my child, which is why we mostly stay home rather than take him to places that we know will be difficult for him for whatever reason. You really have no idea how much that sucks. It would be nice, though, if people would generally be a bit more compassionate and understanding of those who experience life differently that they do. I get that from the outside looking in, people with mental disabilities sometimes look like spoiled brats throwing tantrums, but I assure you, that is not the case at all. An autistic meltdown is an absolute loss of emotional control /inability to regulate that is not purposeful or driven by superficial needs (like a kid who wants a candy bar/toy in a store and his mom says no). Imagine how you would feel if, in a moment of confusion or fear, or a very slight change from what is expected, you were all of a sudden overcome by such strong emotional feeling that you could not stop the torrent, even though you knew it was a minor issue. Imagine the worst moment/day of your life and think about how you felt then. Now imagine that feeling overcoming you several times a day, for issues as minor as dropping a piece of food on the floor while you are eating, or accidentally knocking over a glass and breaking it. Imagine those occurrences making you feel the same way you felt when you found out a loved one had died, or you got fired from your job. This is life with autism for many people. It is heartbreaking to experience and we deal with it almost every day. My son is the sweetest, happiest, funniest kid 95% of the time. The other 5%, he is an emotional mess, crying out of control over minor things, and when that happens, he completely shuts down. It's almost like a seizure. It's a 30 minute process to get him through it and then he is exhausted and falls asleep at the end of it (or just super zones out watching a video).
Anyway, sorry for rambling, but my hope is that this information will, at the very least, help shed some light on our world. Best case, people like you change the way they view people like my child and maybe even teach their own children to be kinder to others and recognize when a child/adult is struggling rather than cast judgment.