If D&D are happy to continue the use of 121.5 for training and emergencies, then so be it. I certainly won't complain.
Whilst the frequency can seem a bit cluttered occasionally. I for one wouldn't change a thing. I know a fair few people who are still breathing thanks to the efforts of D&D AND from the help of airline crew up in the clear blue who relayed calls.
The use of 121.5 for practice pans etc will seem annoying to some of those in the cockpits of many airliners, but given the level of stress I've seen being accepted as "normal", extreme reaction to something actually pretty trivial is not surprising.
I see 121.5 from an instructors, GA and airline pilots perspective and in the UK, I think we have a good system, if only we in the big fast things at high altitude could exercise a bit more discipline and cut out the chit chat, mucked up calls and general daftness that leads to most of the clutter.
I have NEVER heard a spurious call on 121.5 from a light aircraft, but I've heard hundreds from airliners. Glass houses and stones come to mind.