I think there are pretty big differences between people in terms of how much sound insulation they actually want. I find that the insulation provided by the single (floor to ceiling) pane of glass in a WeWork office is more than enough for my tastes. I usually leave the door open if I'm in the office alone.

I have never overheard a conversation in an adjacent office. You can sometimes hear what people in the hallway are saying, which doesn't bother me at all.