Im not entirely sure I see your point clearly.
I will agree that more people in 'open' will make the community 'better', but only if the interactions themselves are 'good'.
I've asked in another thread and got no decent reply, so I will ask you ..
"How or why is it a bad thing to allow players to play in solo/group mode?"
Oh I was simply quoting from above poster.
No one is saying people shouldn't be able to play the way they want to play, but "Open Player's" are saying .... "Hey, if you can play this game the way you want to play it, why can't I play it my way?" I think people are missing what the desires of "Open Player's" actually are. And that sucks for them, and people who want to play solo and unhindered just plain old don't get it because they don't understand that these Open Players don't care about their own personal stuff, it's the community itself they crave and care about. Players swapping from Open to Solo destroys that community development.