You're right of course, the IMC requires a lot less training than the IR so it stands to reason that the average skill level of an IMR holder is going to be less than that of an IR holder. A minimum of 15hrs, although many take far more. Sure, the average IMC holder isn't going to do so well if he suddenly has to figure out the correct join for a VOR/DME fix holding pattern for example, but then he's almost certainly never going to need to, that's why it's not in the syllabus.
What he will however be able to do it take off in BKN040 2000, fly a SID, pop through the clouds, fly on top using whatever beacons are available to him, then descend at destination (also BKN040 2000) and fly an IAP to a safe landing.
Seems to me the only people who regard it as a "get out of trouble rating" are those who don't have one! Of the IMC holders I know I'd say more than 50% have used it to the limits of the conferred privileges, but all of them use it regularly to some extent and none of them would regard it as a "get you out of trouble" rating.