Punishing people for being late disproportionately impacts poor and disabled people. ... We might have to wait on other people, or use public transportation, and the more steps we add to the process the more likely something is to go wrong

Most people wouldn't get upset with you if your bus was late or some other unforeseen accident occurred.

This punishment can include starting without people, especially if that itself is framed as a punishment.

Punishment as opposed to what? If 4 people arrive on time and one person is 30 minutes late then you can either "punish" 1 person by starting on time or "punish" the four by making them wait. This doesn't even include people who just may not show up at all.

In small groups the best solution is to talk things over with everyone and get an idea for what everyone wants to happen, what can go wrong, and plans to mitigate any potential issues.

You're asking the entire group to take responsibility for getting someone there which is unreasonable. Having someone pick them up doesn't mean they'll be ready to go. Once they get used to being picked up, you'll be back in the same spot. If someone is incapable of managing time, not a moral judgement, then there is nothing other people can do to force them out the door.

For large groups, most things do not need a strict starting time.

Most things do actually need strict starting times. If you have more than one event/obligation in one day then it's damn near impossible to get to everything on time if you can't know when they start.

If it is a large group and it requires strict attendance then you brought hierarchy into it long ago and ableism

I have autism, I need a set schedule to function. The kind of wishy-washy with time system you describe would be hell for me. Hierarchy removes the uncertainty in making decisions and I find it easier to work in non-arbitrary environments. I understand your perspective, please try to understand mine.

At the end of the day, we "punish" less people by just sticking with a set time. I get that this system is worse for you but it benefits more people as a whole including other ND people. If you're consistently 30 minutes late, just plan to arrive 30 minutes early. If you think its reasonable for everyone else in your group wait on you, surely it would be acceptable for just you to wait. At the very least don't get upset when everyone else decides to just go.