I think you are assuming by downtime I mean the old "wait around doing nothing, waiting for mana to regen" or "wait 10 min on a flight path.
An example of the type of downtime I am referring to is something like the fishing system in
Threshold, a text mud. In Threshold, the fishing system basically breaks down into the following actions (after you have set up your rod and reel with line, appropriate bait, hooks, etc):
1) casting your line (either near, medium, or far)
2) reeling it in slowly (the number of times you have to actively reel in depends on how far you cast)
3) if you hook a fish, there is a whole process of battling, reeling in, tugging to set the line, etc.
But the key is, you have to wait a certain period of time (more than 1 minute) between “reel ins.” As a result, most people wait a couple minutes between reel ins just to be safe, and that gives them lots of time to chat between actions. The only time they are super engrossed is if they have a fish and it is fighting them a lot. But even then, output goes to the room, so everyone else there is rooting them on.
When people fish, they definitely feel like they are playing the game the whole time. But there are periods of non-intense activity that make socialization possible.