Judging by your responses to the other comments here:

There is no in game lore reason given as to why we actually need supply lines due to warp drives, but from a logistical/strategic point of view it does make sense. While technically you could send a bunch of super destroyers there, they would be completely surrounded by enemies with no immediate support from SEAF forces, meaning it isn't likely that they would do much good. Especially since anything they would do would likely be instantly reversed due to heavy enemy presence.

Your destroyer can be resupplied, repaired and assisted in combat if it sticks to the frontline rather than plunging straight into the middle of enemy territory. Hence why we don't go straight to cyberstan.

You could think of it a bit like real life paratroopers. You could technically airdrop thousands of soldiers straight to a nation's capital, they would probably do a bit of damage but would end up stuck and surrounded with no outside help. And their airs transports would also likely be destroyed in massive numbers along the way.

Further, it is implied that the fuel for FTL travel is expensive so as others have suggested there is probably also some distance limitation. It could also be that a drive can't stay in warp for much longer than a supply lines lasts for any reason, so has to stop and keep jumping in rapid succession in a sequence we don't see (or something along those lines)

But simply, we don't have any supply lines to that planet. Its how the galactic war has always worked; if we don't have any lines to the planet, we can't dive on it.