yeah, that's mostly correct, but i don't see it as a barrier. i don't think an elevator needs to be slammed down next to every staircase. if there's a way in, and a way out, i consider that a win. will i lose maybe 5 minutes because the accessible entrance is not in the most convenient location that day? perhaps. but it's just that - an inconvenience.
on the staff support: i don't really see any problem here at all. in fact, i think the service that the staff provides is truly excellent. most lines have nearly level train-to-platform gaps, but if i feel like i need a ramp, i can ask the attendant at the gate, and they will arrange for someone to quickly unfold a portable ramp when the train arrives, and for someone to do the same at the destination, exactly where i arrive. (coming from the US, can i imagine this level of service at any US city? uh, yeah, no.)