But if by "socialism", you mean "what goes by that label in Scandanavia", then probably no, "collectivist" doesn't fit. It's just somewhat more government services than the US has, at the price of somewhat higher taxes.
I'm saying that socialism, as practiced in Scandanavia, is not collectivist. That means that, no, collectivism does not "subsume any definition of socialism you could ever reasonably give".
Any who, I really think the definition of "Socialism" and "Socialist" require an overhaul in our current societal climate. I'd say that back when that ideology was conceived, people saw people in general and themselves as barely more than "resource" cogs, and that the rulers or state had some sort of "effectively-divine" right to rule them. I would argue that civilized and connected society has moved past that, to the point that anything remotely close to actual socialism or communism would be equivalent to totalitarianism in people's minds. It would be seen as barbaric, and contrary to people's right to exist.