The neutral zone coverage wasn't to blame for that goal. The Devils forced the play wide and Siegenthaler contained the puck carrier to the wall with Bahl supporting, which was played fine. The breakdown is Timo letting the cross-ice pass through the slot and Bratt floating and puck watching while Cozens walks in behind him.
5 guys with their backs turned to the net front and weak side is a recipe for disaster. That's youth hockey shit.
The Devils transition offense is also partially to blame. You can see Timo and Bratt are more focused on gaining puck control and turning the play up ice than defending.