Individuals are more productive than groups, especially large groups, it's shown that working alone is almost 30% more productive—but is it fun? “Group brainstorming, over a wide range of group sizes, inhibits rather than facilitates creative thinking.” It's not just that groups produce fewer ideas, they result in fewer good ideas. Equally so with suspending judgement vs critiquing at the end, while suspending judgement produces more ideas, both produce the same number of good results. Lastly, creativity is not original—ask a bunch of independent groups to brainstorm on the same topic and you will likely get many of the same ideas.
https://medium.com/galleys/brainstorming-does-not-work-6ad7b1448dcf