You're speaking as a low level captain.
Once you're a higher level fleet admiral, you may feel it is unfair in the opposite direction.
The enemy "commander" rarely takes the meta leadership and industrial skills to maximize fleet power, instead they tend to pick up large amounts of combat skills, basically becoming little more than a uber-ship officer that super-charges their flagship power by maybe 30-50%. Don't be them.
A 400 DP battle, if both teams of officers are equal in level & number and all else is equal, gives 200 DP to each side. As others point out, if the enemy commander has better/more officers than you, they may get up to a max of 240 DP and you only get 160 DP. This forces you to rush to capture 2 objectives just to get up to 200 DP yourself to try to level the playing field...or does it?
Pick up Support Doctrine & Derelict Operations, save yourself the $20k - $30.6k per month on officer salaries by not having any, and you can field 285 DP worth of ships at the battle start versus the enemy's 240 DP. Pick up Best of the Best too, and you can field 357 DP worth of ships.
By late game with good leadership/industry skills, the only unfair fights I tend to get frustrated with are when you get ganked by a horde of max ship fleets all clustered together into 1 massive battle. Yeah, my ships are good, but they do suffer PPT attrition when they've each got to kill 8 or more enemy ships a piece. A bit unfair when I'm limited to 1 fleet but the enemy can send a dozen....thank you Nex for Detachments