The power bar is far from pointless, the amount of power needed depends on the situation. The new shooting system is designed to make you think like you would when playing for real. 20% power for example will offer a different velocity depending on a number of factors(ie pressure from AI, stats, momentum, angle of approach).
Its crucial to look at the position of your player and the ball when taking a shot, if you want more of an angle cut in slightly or push up on the analog, this will also result in more curve for players with high stats. You an also achieve a harder shot by pushing harder on the analog, push forward in the desired direction and the ball will travel with more venom. The shooting is very contextual so its hard to explain what to do, its something you just feel in time and the variation you can achieve is better than any pes game before.