I have only flown with TCAS for the last 3 years and even with the odd false alert or wrong sector indication, it is far, far better than just relying on the Mk1 eyeball.
The wannabe (or ex) fighter pilots need to remember that not all Mk 1 eyeballs are equal and a great may GA pilots are of more mature years - are spectacle wearers (possibly bi or tri focal) or just have less than perfect eyesight. Add in creaky or arthritic necks and you have great potential for degraded lookout.
There is no reason that all flying machines shouldn't be equipped with a transponder at the very least - you wouldn't go out driving at night without your headlights on. Remember it is SEE and BE SEEN.
Allow those with TCAS to see you even if you don't have it fitted yourself.
The system I use is a simple display but it has an audio alert - no RAs or anything, just distance and clock code - but it has helped me see aircraft far earlier than I could have noticed/identified them with the naked eye.
Technology might not be the absolute solution but it goes a bloody long way towards it.