The issue isn't carrier spam, its Sparks.
Sparks do multiple things that, in critical mass, make them absolutely broken.
A) They have shields. Now, five sparks having shields doesn't matter because they get bursted down, but when you have 50 sparks, it gives every Spark a chance to breath, which allows them to regen shields... which essentially makes them unkillable, unlike most other fighters that run on armor + hull values instead.
B) They have Burst PD, which is THE best anti fighter and missle defense... with 5, not so bad, with 50 Sparks, this translates to disabling all enemy ships of two of the most effective weapons the AI can throw at you. Pilliums, Reaper, Astropos, Bombers; all of them are disabled by the swarm of Sparks.
C) Burst PD, unlike normal PD, is actually effective at both defense (point defense) AND offense. Which means when you let Sparks control the battlefield, they are like a swarm of bee's. Burst PD on 5 Sparks isn't too bad as it never really breaks shields, but 50 sparks spamming down a single target is like 10 frigates firing at your ships simultaneously every few seconds. That wipes out almost everything in the game except Ordos. But when you get 100, or even 200 sparks? Its essentially game over for everything you fight; even Radiants have trouble against this, and they have some of the best PD for a Capital.
D) Finally, they cost NO CREW. This means even if you suffer losses, there is no downsized to this strategy, unlike Talon + Broadsword spam, which is good but has heavy attrition costs after the battle is over.
All of this coupled together makes Sparks very good at early game, very good mid game, balanced for late game, but ONLY in limited numbers. Once you hit critical mass levels (200 sparks, which is 20 drovers) then its essentially game over. You have won; nothing can stop you. Bonus points if you have 10 level 20 carrier officers and put them on 10 of the drovers.