When a group of people is assigned a task they never had to deal with before, they often start with brainstorming. So you have a number of folks who typically are not exactly knowledgeable about something, but at the same time try to agree on an approach for dealing with it. So they start with a discussion on what to do, who should be assigned what activity etc.
The problem is, that this is not brainstorming. It is group of people talking about something that they do not know much about. So a lot of assumptions are made, often not even consciously. People will simply extrapolate their past experiences into the new topic. But this approach does not deliver particularly good results.
The relatively obvious problem is inefficiency. Instead of the whole group talking 15 minutes about something, prior research by just a single person would have produced at least the same result. (Well, probably a better one.) The bigger problem, though, is about effectiveness. In other words: The result of the group discussion will usually not be a truly good solution. Again for lack of research and knowledge.
From a team dynamics perspective there is another problem. There are people who tend to dominate such free-floating discussions. Apart from personality, the folks talking most are usually those that know least about the subject. Because those that understand things at least partially, know that it is not so easy. But there is no time for careful deliberation during such a meeting. So decisions are made based on the least helpful content and the people who know best go out of the meeting frustrated.
Luckily, it is very easy to overcome this. Just task people to do some research on their own before the meeting. You will have a much more thoughtful discussion.