The same is true for military assist modules...
Sort of half-true. In the early to early-mid game a ship-assist oriented military starbase with a good handful of small or tiny fighters can substantially increase their power. With Starbase Fortification, a starbase can usually fend off anything up to two or three grouped medium class ships. It's in the late game that they're utterly pathetic, and unless you can seriously press an advantage in the early-to-mid game phase it ends up being a worthless investment.
Take Korx, for example. One of their very first starbase assist modules is Defense Jammer, which adds +2 damage to EACH damage type on a ship. Every ship in the radius of that starbase has +6 total to damage. That's a HUGE boost in the early game, and can easily ensure victory for any ships in the area.
The biggest problem with the starbases is that it's too much for too little. I jam ten Constructors into a single Military starbase and I get, what? +10 damage to all ships in the area, +15 defense to a single damage type, maybe a few damage modules for the Starbase itself? Back when Constructors had no maintenance cost and I didn't have to worry about going bankrupt if I had too many non-combat ships floating around, sure. But now it's simply not enough for the cost of the Constructors. I could've built another ship for all that, and now that I have to worry about the bloody ship maintenance of the constructors I literally WOULD be better off building another ship, unless I've got Xeno Ethics and selected evil so I can skip the starbase module-installing fees. Even then it's highly questionable.
Starbases in general suffer from having a radius that's too small, an effect that's too minor, a prohibitively expensive price tag. The only exception to this rule that I've found so far is the Korx, who get very strong starbase modules in the early game which actually make them viable to use. For all other races though, it's simply not worth it. Ever.
I would be happy if they would simply make starbases able to fleet up using your logistics level. Then I don't have to "guard/sentry" ships on top of the starbases separately. Or not even have them in a fleet, but at least be able to dock ships at the starbase
I'll tell you right now, if Stardock made it so I could dock ships at a military starbase and have them repair the ships like I can at a planet, I'd be on them like white on rice. That would be
sexilicious.