Sure, there'll also be plenty of battles in which one side completely outclasses and/or outnumbers the other, but they wouldn't be anywhere near as interesting to play without specialist victory conditions. As such, ACTA doesn't waste anywhere near as much time trying to run them.
Actually, it does. But it also balances the victory conditions.
Look in the Rulebook at the scenarios
Battle of the Line and
The Long Twilight Struggle.
These scenarios are representative of the two fleets involved because it shows a roughly equal 'force' (a half-dozen of the race's primary capital ship units) being sent against one another, but there is such a disparity in their relative power that victory is merely a matter of survival for the weaker side.