There is a thing people say about how the word no is a complete sentence. As in, no I will not be doing that. Or no, if you do that, I will not be applauding you or supporting you. It of course doesn't mean you always get your way. There are moments when it is useful to be in brainstorm mode. To say, oh great idea but what if we did this instead. If everyone is trying to figure out where to eat dinner, then just saying no is not helpful. (Unless you are saying, no, I'm going home.) No to Chinese but yes to Mexican is helpful.
But there are times when the no itself is important. No, I do not approve that message. No, I am not okay with this. No I will not tell this person about your great idea. No. No. No.
No, of course, does not always mean you get your way. But showing up to say, no it still powerful and important. When we are taught history the focus is often on what the people with the most power did. And that sometimes elides the complicated discussions they were having, and the people outside the room who had thoughts and feelings too.
Even when the powers that be continue on with their choices, joining with others to say no is useful. It reminds them you are watching. It reminds others who though they were the only one who hated it, that they are not alone. And it can help move later decisions in different directions.