I think design by committee is a sign of lack of trust. If a designer has the experience and the presence of mind to gather all the information from the people closest to the problem, they can then put their skills to work to solve that problem.
I ask for input a lot to make sure I’m understanding the problem, but if the design doesn’t work, that reflects on me, the designer. The committee should respect and trust their designers to make it work.
Some good advice from Keith here, both for designers and their teams.