Going by what I can recall, while there's probably some logic to carriers simply because a shift to smaller, more powerful line combatants makes it less viable to use said line combatants as motherships for small craft, which are somehow remaining relevant, I'd argue that the focus should really be on something closer to Escort carriers rather than anything that could be termed a fleet carrier (no matter how you're using the term). Having trouble articulating the specifics usefully at the moment unfortunately.
Maybe I can help.
The old meta in space combat was the bigger is better. A Dreadnought is unbothered by Cruisers (Heavy or Light) because it has the firepower to blow through the Cruisers Kinetic Barriers and the volume to mount and power enough Kinetic Barriers that the Cruisers can't do the same. The same logic applied to Cruisers vs. Frigates and while Fighters defied this paradigm with their Disruptor Torpedoes that only applied en-mass which is only a concern for defensive battles as transporting Fighters long range is a significant logistical burden.
Since humanity arrived on the scene a number of changes have arisen. The first is of course Carriers. Carriers were almost certainly intended as a dodge around the Treaty of Farixen as they are
basically Dreadnoughts but missing the spinal gun (and almost certainly designed with refitting on in mind). However despite that Carriers are a potentially meta disrupting advance as they allow for the mass transportation of Fighters to the battlefield and thus allow for the leveraging of numbers in torpedo vs. GARDIAN duels.
Revy Shepard meanwhile has proven far more disruptive to the meta then that. The first major shakeup was her creation of Arc Reactors. This low cost high density energy source changes things. First it allows for massively improved Kinetic Barriers bumping up the shielding of pretty much any unit equipped with them, secondly it increases the rate of fire for larger MACs since they no longer need to charge, thirdly it increases durability by distributing the ship's power generation rather then having a central reactor to destroy. Then came the Repulsors which double a warship's FTL speed and (IIRC) conventional speed compared to the traditional anti-matter enhanced fusion torches used. This dramatically increases the strategic responsiveness of our fleets as well as their tactical flexibility.
The list just goes on after this. Improved Warheads to punch through those enhanced shields, Arcane Blur (albeit we purchased rather then created) to decrease accuracy, Biotic Warp inspired shielding to counter our improved missiles, faster firing (10x) railguns for massively increased conventional DPS, lasers for stripping away enemy shielding by targeting their emitters, enhanced targeting VIs, improved Eezo Drive designs for faster FTL, hyper-modularity for rapid upgrades, improved material science for superior armoring and structural integirty, Multi-Core Eezo systems for unlimited FTL endurance, proliferation of cheap drones and micro-missiles.
We are entering an era of a radically changing meta and large scale starships are just a poor response. We can see this in nature; smaller creatures tend to weather mass extinction events better because by their nature they can more quickly adapt to their changing environment. Similarly Dreadnought scale starships are a significant investment of time and resources that could very well be obsoleced before they even finish construction. Meanwhile Frigate scale starships are vastly cheaper, faster to build, and their loss through either combat or obsolecance is far lesser a blow. While this is partially mitigated by hyper-modularity allowing for easier refitting as new technology is invented it doesn't change the fundmental issue that investing in a few expensive ships is a poor choice in this rapidly changing situation.
This is further emphasized by the fact that while things are still balanced
right now at the high ends of the meta indications are leaning towards a shift away from the current supremacy of defence over offense to the supremacy of offense over defence we are more familiar with IRL. That is what lead to the death of capital ships, outside carriers whose saving grace of remaining outside the field of combat is limited to oceanic warfare, in OTL. When a handful of comparatively cheap torpedoes, and later missiles, can sink even the most defended ship investing in a multitude of cheaper ships over fewer expensive ones becomes the obvious choice.
So with all that in mind Escort Carriers while individually less capable then Fleet Carriers are likely a safer investment. They are smaller and cheaper so the loss of one is less impactful to the overall fleet. They are smaller and cheaper thus the logistical costs of keeping them updated are smaller resulting in less lifetime overhead. They are smaller and cheaper so can be built up into a larger fleet at the same cost allowing for increased strategic flexability.
