Paris is ancient and built on a bunch of hills, there are quite a few places where retrofitting the city to make it more accessible would be easier by rebuilding the whole thing than by making changes and that's not going to happen. Amsterdam has an easier time of it, not quite as old, though old enough that that isn't a big factor in the difference, the good bit is that it is mostly flat (other than the canal bridges, some of which can be pretty steep). Even so there are areas of the inner city that would be hard to navigate in a wheelchair.

Stockholm wasn't exactly built last year either.

True, but like Amsterdam it is mostly flat, right?

Having lived in both Stockholm and Amsterdam, I can assure you that Stockholm is not at all flat like Amsterdam!

No idea about how easy either city is to get around with a wheelchair. Pushing a fully loaded double-stroller is no problem for an average-sized, ablebodied adult in any of them.

Hard to tell for me, after decades in Bergen my sense of what people consider hilly is skewed.

Just the name of this city is an indication