"Group" rides vary from one end of the spectrum to the other. Some will be conversational pace rides, some will be training, some are novices, some are well experienced, and all of them will be different.
I personally enjoy really show paced conversational rides most of the time, but also enjoy joining a group who are slightly faster than myself from time to time just to push and see what I can do.
The club that rides out of the shops I have close by are all fairly fit, and quick IMO even on the "B Social" ride. I asked about, and helped create a novice paced slow group for club nights so that new riders could learn about group riding and not feel so intimidated about (or simply join due to obliviousness about) the average speed requirements for the groups. It has helped a lot for the club and for me. I have people to ride with for a while till they get faster, and it has helped increase the number of new riders sticking in and moving up to the faster groups.