Those 2 points are exactly correct. Which is why they have a weak power play. It scores much less than it should because the players don't execute it correctly. There isn't enough movement by players without the puck towards the net to form screens, jump on rebounds, and to draw the defenceman out, creating openings. There is also not enough driving to the net by the receiver of the pass. There is too much passing around the perimeter, at a distance far out. Too many possessions are lost with too many passes, allowing the defence to get in position to intercept passes, or increasing the odds of a pass going astray, or running the clock too much, making The Blues need to shoot a poor shot in desperation, just to get a shot off (without screens, without teammates down low to grab rebounds, and with the goalie having perfect sight lines and being perfectly square to the puck, a telegraphed shot which hits him in his belly. The Blues' 21% for the regular season was about average for The NHL. But, this lineup is capable of doing much better.
The Blues had better win Wednesday, so we don't have to know they didn't win The Stanley Cup because they couldn't execute what their power play coach told them to do, OR because they couldn't get a power play coach who could get them to use the proper strategy. Either way, it's a shame after waiting 51 years for them to have a real opportunity to win it all.