I'm not sure where you're getting the "canonically not a military force" bit. There have been a number of wars in canonical history. Who did the fighting? Starfleet.

I think it's more accurate to say that the Federation of Planets wasn't militaristic, not that they didn't have a military or that Starfleet wasn't their naval equivalent.

And yeah, it's not conventional military fiction which usually revolves around actions during a war. But it's still military fiction in the sense that nearly all the characters are in the military and doing missions for the military. It just happens that the government running that military is at peace most of the time and uses its military for peaceful purposes when it's not actively at war.