> presenting an idea and being told that it isn't good (by someone presenting no alternative) ... isn't something someone should need to deal with.

I might be visualizing a different conversational domain than you are, but I'm not sure about this.

For example, when you build a bridge, there's a clear, objective line of quality somewhere above "the bridge stays standing." If I know enough about physics to see that your bridge won't stand, that doesn't mean that I also know enough about architecture to propose my own bridge -- but it doesn't have to; the knowledge that design X is fatally flawed is useful in its own right.