I think it is an idea that alienates people who actually want and can achieve pragmatic change and attracts people who have passion more than sense, and ultimately either accidentally or intentionally (by someone) ensuring that the broad motivation to make positive progress is derailed by the disorganization of a movement that doesn't really know what it's about or what it wants.

It is vague "on purpose" because the things which actually need to change are subtle, require understanding of specific circumstances and deatails, involve compromise and human understanding of the failings of people, and generally nothing else fits on poster boards.

If I were a little more paranoid I might be suggesting that the bad slogans of protest worlds are actively being encouraged by sophisticated opponents of these movements in order to ensure that they achieve nothing.

If someone really wants change, they should say it instead of accusing people who question them of not understanding their poorly chosen message.