I'm having the same problem. its like im playing wack a mole with the planets outside of the core. in my current game every space battle has at least one lukrehulk, and like 100 smaller ships

Some advice maybe for you: I build now the Mandator II and a fleet around with venators and a lot corvettes to counter the fighter/bomber spam from the CIS. This is my core defend fleet. I also conquerd the last CIS planets in the core. Now i build 1-2 fleets to expand slowly but save into the outerim. Still losing planets near the core. I have now 41 Planets under my control. CIS has 62. So theres a lot of work still to do. You need to build and expant realy fast to survive. And do the missions to get more military value plantes like Corellia and Rendili.

Thanks for the tip! I ended up deciding to restart with the medium map to get a better understanding. I've been doing more missions now, especially since it's easier right now without the constant attacks.

I've been doing hit and runs in the From the Ground Up GC on Colossal with the GGC Submod, to get better at it FotR. It helps as there are more planets between me and them that I can get a secure feel for the game.

They need to add several point-defense light laser cannons to the Acclamators and Venators for anti-fighter defense.

Acclamators have 24 point-defense light laser cannons according to legend, canonically, 'The ship was ringed by a series of point-defense laser cannons.' They should also have faster shield recovery than most other ships. as they have multiple shield generators throughout the ship.This is in my opinion.

Venators have at least 52 point-defense laser cannons for anti-starfighter purposes. They should also have 2 firing abilities. one for stronger power and farther range but slower fire, and one for rapid fire and quicker aiming.

I've definitely had similar issues myself at times during the campaigns I've played through, at its core I feel the biggest 2 causes of this are that the AI is always fully aware of what you have at every planet, so it know's how much to bring to have a numerical advantage (which if it doesn't have it simply won't attack at all) while at the same time it often doesn't care so much about holding to on any one single planet of its own, so doesn't mind concentrating a larger portion of its forces in to one or a few super larger fleets, where a player would often prefer to divide their forces to try and defend from multiple directions.

This has always been present in the base game's AI but as the mod scales things up quite a lot, its much more visible.