That's not a philosophically sound position. For one accustomed to doing that via power clearly power would be the best monitor. Could one experienced go on perceived effort or use another metric? Sure. I have down taped over training to see if I could hit specific numbers. But to assume that because the event is timed then one shouldn't track power really seems to be out on the edge. If you or your kid doesn't like using power that's fine. But to imagine that it is, or will become, some sort of universal thing is a bit silly at this point. Power training is so valuable they're trying to bring cost and functionality to running and crew as well.