Muds wouldn't have. The entire point of a mud is that it was uninstanced, interactive, communal play. Sprawl or PK were the mud solution to the problem of over population. The less willing you are to do either of those the more instancing becomes a third solution.
I sorta wish I'd played AO. I remember we were raiding in EQ and one of our guys was in the beta and we'd give him shit for it -- and he'd always talk about what a clusterfuck the launch was going to be. I barely even knew it existed, tbh.