IME, a non-hierarchical workplace is the most dangerous place not to be a yes-boss. This is because responsibilities are often assigned without any regard for whether that person has the skills or mindset to do the task. Often the question that needs to be asked is not "am I the right person to do this work" but "is this other person the right person to do this work?" Maybe you'd think that's none of my business to ask, but it often falls to me to go in after someone who's not qualified and try to build on that work. When it takes longer than it should, non-hierarchical organizations often frown on surfacing what the cause of that was.