Well said.The spirit of street photography is to be bring out the humour/irony/truth of life in its rawest form. It's about capturing people/places at their most candid moment. By going around in a big group,
1) you attract attention of the subjects so nothing's candid anymore
2) you go slower and end up with less unique perspectives because everyone's floating around the same place
It's like holiday travel. The bigger the group (think tourists hauled from attraction to attraction by the busload) the more mainstream/less unique your experience. Think about it- if you were taking a photo from a certain location, it's unlikely for some photographer in this street photography group to go to the opposite side to try for a different angle. Because then you two get into each other's frames. So, everyone ends up shooting more or less from the same perspective and ends up with mediocre shots.
At the end of the day, street photography is a lot about capturing the Moment-- and it's brief and fleeting so you need to be fast when it happens. In a group, you lose that ability to be spontaneous.
The best street photography I've ever seen and done myself have all been the result of solo trips.
Bottom line: this genre of photography is tough as it is. Don't make it harder on yourselves.
My two cents.