Here are the problems with the #1 PP unit as I see it:
1. Marner and Rielly are the only ones moving the puck, or moving in general. They're too stationary.
2. Puck movement mainly works through a triangle of Rielly, Marner, Matthews. Predictable set-ups.
3. Rielly isn't a threat to score from the point and never shoots, which allows the PK to collapse and focus primarily on guarding Matthews and Marner.
4. As Matthews is mainly the target man, PKers have merely to close him off. Marner does the best he can but ultimately can only look to pass to a covered Matthews, feed it down low to Tavares, or shoot into traffic.
5. Tavares is wasted down low. Good hands in front of the net, but needs to be in a position where he's more involved.
6. Kadri does literally nothing but stand in the middle of the ice the majority of the time.
Almost every powerplay is Rielly, Marner, and Matthews playing catch along the outside with Marner eventually trying to thread a pass through the eye of the needle to Matthews or Tavares. Matthews is always covered and Tavares is usually in too tight to do much with the puck. The second unit at least seems to have a lot more movement when they get set-up.