The ADSB system could be used to monitor all traffic anywhere in the world - that's how sites like Flight 24 work. They aren't used now for NOTAM level activity because they are prohibited from being used that way. It's also sufficiently real time (I think typical updates are less than 60 seconds apart) to track ground vehicles at large airports.
Having checked the NOTAM for your airport prior to departure if you have a wheel's up on the runway after they depart, how does the pilot know about it?
Either ground the antique or put in an electrical system. The GA system kills more people every year than the MAX did, and too large a number of them are from mid-air collisions, including professional and expert operations. ADSB is easy to adapt to track local traffic - costs about $100 in hardware to use a software defined radio and a single-board computer to discover the traffic and a small LCD panel to show proximity and path. No doubt "certified'" systems will cost more because they can. GA pilots also fly into power lines, as recently happened at Gaithersburg. An ADSB broadcast having that as an obstacle would very likely have avoided that problem.
It is a problem that the FAA has been dragging on ADSB - but I think it better to focus on an integrated solution to the majority of problems than spend a similar amount of effort on what is essentially a dead end technology. Improving NOTAM is trying to keep the printing presses running for delivering the newspaper so that readers can check how the market is doing.
What is funny (freaking hilarious) is that the FAA has mandated that all model airplanes and remote control drones transmit an equivalent of ADSB of not only the location of the item, but also the location of the operator. Somehow a model airplane is more regulated for that aspect than manned aircraft are. This in spite of 0 fatalities from hobbyists in at least the last 50 years vs an average of 1 per day in the US for manned GA. However, there is a danger - as demonstrated when a cop set his drone directly into the final approach to an airport, a cop meeting all the FAA operator requirements, including an observer, suggesting that law enforcement not be allowed to operate drones. Best part - that cop was stationed at the airport. No NOTAM for that operation, but had the drone had ADSB-Out and the small plane ADSB-In the collision would likely been avoided. Had the plane had ADSB-Out the cop could have been alerted to the plane coming in or the software in the drone designed to avoid the collision.