With Starfleet it sure seems multidisciplinary, but they still are the 23rd-24th century equivalent of the military.
We've SEEN the 23rd-24th century equivalent of the military: the Klingon, Romulan, Cardassian and Jem'hadar fleets in particular. Those organizations DO emphasize combat capabilities; their ships are compact and utilitarian, lacking amenities or advanced scientific laboratory equipment or sensor capabilities. The largest ships in most of those fleets are designed purely for combat; the largest ships in Starfleet are designed primarily for exploration.
Wait, how do you know how much of their ressources they devote to all that ?
Primarily, the fact that various individuals have said at various times that most Starfleet vessels are NOT designed purely for combat. By the 24th century, personnel assignments are being made with the crew's comfort in mind -- e.g. spouses and children being brought on board -- both to the exclusion of other tactical considerations and the bemusement of just about everyone in the universe whose space forces ARE standing militaries.
Secondarily, it's obvious that Starfleet is incredibly active throughout the galaxy even in peace time: when their ships are not in combat, they are mapping new sectors, exploring alien worlds, charting solar systems and comets, cataloging gaseous anomalies, etc. They spend about 10% of their time fighting or preparing for a fight; unless combat operations are ten times as expensive as their scientific programs (which seems VERY unlikely considering the nature of their weapons) it means that that their science budget is at least ten times larger than their tactical budget.
So basically your counter to every element of my list is "nope" ?
Did you expect me to counter them with "yep"?
Entirely of scientists ? Is Uhura or Sulu or Chekov or Kirk or Riker or Worf or Yar or Rand or Sisko or O'Brien or Paris or Scotty or Archer or Mayweather or Sato or Reed a scientist ?
Hell, the only people that's even a question for are Worf and Yar, because they served as TACTICAL officers.
And yet even Worf appears to have relatively advanced knowledge of both computer science and electrical engineering. In "One Little Ship" Sisko asks him to "plant a computer virus" in the warp core subprocessor that would effectively destroy the ship, and earlier we see him and Nog reprogramming the Defiant's fire control systems basically by hand. Even earlier, in "A fistful of Datas" he's able to manufacture a personal forcefield (In a cave! With a bunch of scraps!). Worf may be a warrior at heart, but like most Starfleet officers he has the equivalent of an advanced degree in at least two different fields. Basically, he's a scientist who likes to experiment with weapons.
As for the others... I'm amazed you even asked.
Did you just argue that the Federation has a military branch to combat its enemies, by which it is surrounded by almost all sides it seems, but that despite the battles we saw in every iteration of Trek so far fought by Starfleet, that we somehow never saw these guys or their ships ?
Yes. Primarily because
1) "these guys" probably don't
have any ships, and wouldn't need them if they did. Most battles appear to be fought on the ground anyway. Probably in the same way and for the same reasons that the U.S. Air Force doesn't have any space stations and the U.S. Army doesn't have any submarines.
2) We never saw or heard of the MACOs either until Archer specifically asked for a squad of them to be assigned aboard his ship. If the MACOs are still around a century later -- and they almost certainly are -- Starfleet has even less reason to refer to them or request their presence than Archer did.
As a matter of interesting parallels: Starfleet vessels appear to be primarily exploration ships with advanced combat capabilities, while Klingon ships appear to be TROOP TRANSPORTS with advanced combat capabilities. The Romulan warbird is implied to follow a similar design philosophy, and even Ferengi Marauders evidently double as trading vessels.
It seems that advanced races rarely build starships purely for the purpose of fighting other starships. It's not that it's impossible per se, it's just highly impractical and expensive.