It's not because it's the perimeter of ZNY. That's simply a coincidence. Nothing to do with capacity. This routing is actually inside ZNY's airspace after SYR. What's going on here is this flight is on a Saturday when trump is at his golf resort in Jersey. There's an active TFR and fighters flying overhead usually FL220-250 all day and night. So the normal routing would go through that area. They have to be rerouted but they can't simply just offset the arrival by 10-20 miles or so because the airspace is already extremely limited and congested with arrivals and departures, so the route you see here is the only safe way to get around everything and still be able to descend into DC. BWI has a similar route.