We could debate this RT stuff; probably there can be no hard positions on it.
However, I do think that currency affects it. I hear some dreadful RT every time I fly, and all of it sounds like pilots who either rarely fly, or are deaf. For example, if somebody says "over" at the end (shortwave-style amateur radio stuff) how much normal RT have they listened to? It's really basic and obvious.
There is also ATC to listen to. British ATC is normally very proper and very professional - so different from VFR services elsewhere. (IFR ATC is pretty good in most places). So a pilot who flies reasonably regularly must be wondering about whether some phrases are right.
I know little about the microlight scene but otherwise I think really bad RT tends to belong to pilots who are only just hanging in there. Training won't help them much.
Regards a Mayday relay, I recall this is another valid option: a man in a life raft could make a Mayday on 121.50 using a handheld radio, and an airliner could relay this as a Mayday relay call. I carry a radio and a handheld GPS for exactly this reason.