"Does that mean you still don't accept that it's beneficial in uncontrolled airspace as well?"
I believe that there is value in having appropriate mechanisms for the relevant airspace. If Mode-S is the most technologically and cost effective solution within controlled airspace then that's fine. A bit like taking the train really - as a passenger I find some comfort in the idea of signalling equipment, a professionally qualified and trained driver and control/monitoring systems. Rather like in a commercial aeroplane really.
Likewise, considering an uncontrolled airspace analogy, I accept that driving along an autobahn at 200km/h, surrounded by other drivers who may not be awake as me and who could pull out at any moment is an acceptable "risk" which 'could' be overcome through the introduction of technology but which would dramatically increase the cost of car ownership (e.g. every car could be fitted with a simple form of Mode-S/TCAS connected to the accelerator/brake).
If there was a simple, low cost, feasible, reliable, fully interoperable system that could be used autonomously in uncontrolled airspace, then yes that would be a great idea. Unfortunately, the options seem to be Mode-S (expensive and unsuitable for all GA), ADS-B (more advanced than Mode-S but not supported by CAA) and FLARM (being trialled by some glider pilots but incompatible with CAA/NATS kit).