Two ideas are better than one. But one quality idea punches a better blow than ten irrelevant ones.
The quantity idea can always come along with quality idea. Thus, a debate between quantity vs. quality can be unnecessary. It only matters when there are more trivial ideas that are being suggested than one vital idea.
Although it is true that we can build a tower with hundreds of blocks; but if these blocks are not made with strong elements, the tower would still disintegrate. So to speak, if we can come up with a strong and impactful design, then it is enough to stand on its own and can last long.
In a team effort, a concrete suggestion by a newbie member to a single problem could always outsmart the trivial ideas of the tenure members. In addition, even if we run out of count with the ideas that we have on the table, if there is no differing spot among them, our ideas would still not make the cut.
Our mind is filled with creative and surprising ideas. What we need is time to refine the essence of the many concepts that could be running through our minds and then we can appreciate the efficacy that a compelling idea proposes.
It is not the number per se that is important, it is the impact that one idea can make in building a feasible solution to a complex problem.