You sound like someone who is new to hockey
It's the playoffs, you take what you get. You can say Boucher was falling down, I will say CSKA's PP cost themselves yet another breakaway, it doesn't matter falling down or not, it ended up being a goal. It's not like Boucher dropped down from the sky in front of the CSKA goal.
And yes, when they have a lead Avangard sits back and blocks a ton of shots. That doesn't make them a worse team. It makes them a team that plays a certain way to get the result.
Anyway, if CSKA are the better team, they have to start proving it starting today.