The implication from the first post is that players are either Solo or Open players. This is wrong from the outset. I play in all modes, depending what I am doing. Usually I'm in Open mode, but in busy places I often have to switch to Solo mode to actually get anywhere (otherwise instance transitions can take ages - literally minutes at a time). When I take part in expeditions, there is usually a private group for that (strangely, busy instance transitions don't seem to take long in private group mode).
So, my view is that FD made a very good decision with the three modes.
So, my view is that FD made a very good decision with the three modes.