If a disabled person is waiting for an elevator, especially a wheelchair or bulky mobility aid user, you need to let them in, even if that means you have to take the next elevator.
Go watch the quest for the rainbow bagel, if it's still on YouTube. The guy has to wait as elevator after elevator after elevator is too full for him. Ultimately, he crawls down the stairs and has his companions carry his wheelchair for him. This is difficult, dangerous, and could break his chair- breaking his legs, essentially.
All because people who can walk were too selfish to let him on.
You can squeeze into a packed elevator. Bulky aid users can't. So get out, encourage others to get out, and let them in. You just have to say, "oh, you definitely can't go down the stairs, but the elevator is too full for you to squeeze in. I'll get out to make room for you and take the next one." It will pressure others to help.
This also applies to bathrooms, by the way. "Oh, you need the accessible stall. I can use any stall. Why don't you go ahead of me so that you can use it when it's available."
Standard disclaimer that non apparent disabilities exist and some might need the elevator/stall. If you have trouble with standing, I highly recommend getting a foldable seat or a cane seat. I sit on mine when I need to wait.
