I think it is a simple lack of fish. The entire Delaware River/Bay striped bass fishery is hurting. The bay fishery is and has been terrible for years now. My boat is on the Maurice River and I haven't even thought about fishing for striped bass in the bay for 4 or 5 years. The Cape May charter fleet that wants to fish for striped bass in the spring have moved their boats up to the Cohansey River and are basically fishing the mouth of the river where it meets the bay hoping to intercept whatever fish are left. Instead of simply going straight out of the CM Canal, fishing the lower bay and finding good fishing and giant fish. The Elsinboro/DoD/National Park bloodworm bite was below average to bad this year also.
I'm assuming the OP is looking to fish for the big spawning fish in the spring. If you want to catch schoolies to low 30 inch fish than that still seems to be ok but you are looking at fishing Trenton north. My last decent fish was July 20th on a swim shad above Yardley. Of course that coincides with the start of our 2018 monsoon season. They may have been around even longer or may have never left but it wasn't very fishable via wading. 2017 I had keeper sized fish on pencils in June around Lambertville. You'll certainly need a jet boat or need to be very careful with a smaller outboard in those areas. The shad fishing was very good this year and the smallmouth fishing has been good also ( I've had a great year on big smallmouth ) when it is fishable.