Does seem to be a fallacy with many people, doesn't it? Either you're a wide open offensive team or a trapping team. No middle ground...on much of anything, really.
Boston is successful partly because they insist on having 4 lines mostly comprised of guys who can play both ways and aren't afraid to do whatever it takes. They play a team game that covers all the bases and doesn't rely on the referees granting power plays. Smart hockey, filling the lanes, making good passes, screens, going to the net...fundamental hockey top to bottom, and built from the goal out.
The Caps are a one line team, and it's the third line. The 4th line was a dumping ground, the 2nd line was a confused mix of grinding and finesse, and the 1st line was one of the worst defensive top three groups I think I have ever seen, with no chemistry or finish to make up for it. You had a 3 headed goaltending monster that was being torpedoed by the head coach, and a defensive merry go round that made the rebuild defensemen look like a solid crew.
The Bruins have 9 or 10 guys who are right around that 20-30 goal range, almost all with a pretty consistent, high plus/minus.
The Caps have a 50 goal PP turret, three guys sniffing the 20s, and then everyone else and plus/minus all over the map including some of the worst in the league.
People can poo-poo those stats as not telling a complete story but when you see a massive pattern it means something. You may not say X is better than Y because of a few digits difference in a stat, but when entire teams show patterns that's significant.
If a Benning comes in and builds a team with 10 solid 2-way guys scoring 25-30 goals in front of a d-corps that's true NHL quality, and they go deep in the playoffs and maybe threaten for a Cup, who would complain that Ovechkin is only potting 40 because the firewagons aren't running? Not me.