Honestly, I kind of followed your post up until the above comment where I lost you. I can't wrap my head around it. Did you build these illegal jumps in your own backyard/property? How else can you manage them otherwise? Kind of straying away from the issue here though...
I think this issue falls down to a balancing act for people who enjoy riding trails. By trails I mean DJ spots. In our state, and around our region, there are trails nestled into many "remote" green spaces. In NJ remote doesn't necessarily mean backcountry, but means "people just don't go there much." There is one that has quite literally 30+
thousand hours (or more, impossible to quantify) of work, and has been there for decades. The jumps look like they were constructed by artists or stone masons, and honestly the work is truly artistic. How many on this forum know a spot like that?
The reason why they endure is because they aren't in a place people go, and certainly not in a place with 1000's of passes a week by multi-use trail folks. they police themselves, and injury rates are low. Lots have progression lines, or 411 on a spot that you can progress into the bigger spots. You find the trails by being invited, and when you get invited you dig if you want to ride. If you dig a lot, maybe you'll eventually get the keys to the cables.
I don't like discussing this on a public forum, but I do it to illustrate that there are indeed really amazing places to ride DJ trails in NJ; so many that there is probably one in YOUR town. Is it illegal? Yes. Do I condone it? No, but I understand. Will they ever get bulldozed? Maybe, but it will be because someone broke the rule mentioned above, not because someone without the requisite skill unknowingly "sent it dood."
People building features on public land accessed by thousands of people per week, especially those run by the state (with whom JORBA has a wonderful relationship with btw), are doing it wrong at the very best. To someone who has worked for nearly two decades to preserve and expand legal access to NJ multi-use and mtb specific-use trails as legitimate stakeholders, you are displaying selfish, entitled behavior and giving our entire community a bad name and threatening current and future access.