I don't think the selection of this team was the problem. I don't think changing one player for another changes the outcome much. This team was fairly young and inexperienced but the talent was there. The coaching was atrocious, though. The players don't deserve to go blameless but I can't even count how many times I disagreed with the decisions made by Lowry. For example, your complaint about Sanheim not getting it going, that was in large part because of Lowry. He chose to play Hickett's half the game and gave him a lot of the PP time. When Sanehim got his chance today, the PP excelled.
Why Konecny didn't play more is a mystery to all of Canada, he is a heart and soul type of player that should've played twice as much as he did. I even think Stephens deserved more time with him, they two of them played well together.
Beauvillier and Barzal were too talented to be sitting on the bench as much as they did too, especially in offensive situations. The thought that Strome, Marner and Point could carry this team offensively was shown not to be true right from the start, but Lowry kept allowing them to take 2 minute shifts, and double shifting them. This team was deep enough to play 4 lines. In fact, they were at their best when rolling all 4 lines.