The downside of brainstorming

Today, my boss called for a brainstorming meeting to get ideas from a couple other officemates on what my function could deliver for the rest of the year. It would have been fun to come up with out-of-the-box initiatives, but I was held back by all the worries on feasibility and relevance to what we are trying to achieve at the end of the day. Isn't it that key to excellent execution is FOCUS? Rather making an effort to be creative, I took notes instead. Will process everything later, when I can clearly think about an approach to managing my boss' expectations.