A quick example of why ADS-B is really important, from the perspective of someone who spends a lot of time in extremely busy, congested airspace, often doing unpredictable stuff.
Most smaller (non-airline) planes today use ADSB for traffic deconfliction, and it’s been a huge, affordable improvement for safety in congested airspace. I have a $50 Linux home built ADSB receiver I use with students, and it’s helped us avoid dangerous situations like this F-18 on a Bay Tour.