Ok, to clarify.
Maybe I should re read the release notes, but I thought an basic Modular fort should be close to a cap of regular forts, while a modular fort with III modules should exceed a regular fort. Maybe I read it wrong.
For a fallen spire game, modular forts maybe are a good deal. But for any other game, they just are not. Get regular forts instead. Yes, the cost more, but are much more flexible and allow further upgrades in the research tree.*
*Unless you naturally get either MK III beam cannons or shields (maybe) AND III lasers / missiles (maybe)
*** I say this because the nature of defenses has always been "flimsy glass cannons" which modular forts seem the first exception to. Except, with the natureof AI war, for defense you want greater offense, to prevent the popping of your command station.
Also keep in mind regular forts have vastly, vastly greater range then any of the modules.