This really isn't true. You're making it seem like Washington's key forwards aren't doing anything and are getting dominated by Pittsburgh's key forwards and the depth isn't making a difference in this series. Here's how it actually looks though in terms of pure point production:
Pens:
6 points - Guentzel
5 points - Malkin
4 points - Kessel, Schultz, Crosby
3 points - Cullen, Hornqvist, Maatta
2 points - Cole
1 point - Bonino, Kunitz, Wilson
0 points - Duoulin, Sheary, Kuhnhackl, Hagelin, Hainsey, Daley, Rust, Rowney
Caps:
4 points - Kuznetsov, Backstrom, Ovechkin
3 points - Williams, Oshie
2 points - Niskanen, Shattenkirk, Johansson
1 point - Schmidt, Eller
0 points - Carlson, Burakovsky, Winnik, Beagle, Alzner, Wilson, Carey, Orlov, Orpik
So, we have Guentzel outproducing everyone as not a core player. Then we have Malkin with 5 points, Ovechkin, Backstrom, Kessel, Kuznetsov, Crosby (in 3 games) as core players with 4 points. Schultz with 4 points as a non core players. Pittsburgh with one more non core player in the 3 points category. Washington with 2 more in the non core 2 points group. Pittsburgh with one more in the one point and one less in the zero points group.
Amongst the team's big forwards that would generally be considered their core:
Pittsburgh: 13 points (one less game for Crosby)
Washington: 12 points (or 11 if you want Oshie here instead of Kuznetsov)
Guentzel and Schultz alone have 10 points. Washington's next best two combine for 6 points. Then Pittsburgh's next two combine for 6 points while Washington's hits 4 points. Or for an easier way to look at it:
Pittsburgh's core forwards: 13 points
Washington's core forwards: 12 points
Pittsburgh's depth: 24 points
Washington's depth: 14 points
Pittsburgh's depth is dominating Washington's in terms of pure point production. I do think Pittsburgh's core forwards are outplaying Washington's but I'd say their depth and better goaltending are having far more of an impact on this series thus far than their stars outplaying Washington's stars.