It's very useful to diverge on ideas before converging on a solution. Trying to do both at the same time tends to stifle creativity and lead to less innovative solutoins.
I find the creative process of brainstorming is more effective if I do it separately to refining ideas. Taking the time to brainstorm leads to better solutions, whether thinking about what to work on, planning out a presentation or designing a technical solution. Generally the first idea you think of isn't the best one and it's better to have an array of options to pick from. For a particularly difficult or unfamiliar problem it can be worth doing multiple rounds of brainstorming with breaks and additional research in between to generate enough understanding.
Picking a solution requires a different mindset. When I try to rule out solutions at the same time as coming up with ideas I find the range of ideas that are produced tend to be more narrow and I suppress ideas too early. On the other hand when I have a bunch of ideas it's much easier to evaluate and prioritise them.
I find the same thing with writing; it's easier to start with writing the piece as freely as possible, and then come back and edit it at a later time. If I try to edit too much while writing I get stuck and find it harder to finish. However if I come back to edit a week or two later it's a relatively easy job to rearrange and polish the piece.
This works well in a team setting too; doing a large brainstorm on post-its, then grouping up themes and voting on the most important ones can be a very effective process for diverging and then converging.