Paradox's design disdain towards static defenses is simple.
This is a studio whose foundation lay in games like Europa Universalis, Hearts of Iron, and Crusader Kings.
Notice that static defenses in any of those games will NOT win you wars. They only buy time until your enemy sieges them down, starve them into submission, flank around and isolate, or simply punch a hole through them with superheavy artillery and tanks.
Paradox's design philosophy is well grounded in real-world military theory where turtling is simply not a viable strategy and will only bring a slow death. The only purpose of defense is to buy time for a counterattack.
Stellaris is one of the only titles that opened up to the casual crowd, who are more interested in their own playstyles rather than learning military doctrines that the rest of us HOI or EU veterans already know.
In both EUIV and CK2 static defense can and will win you wars. All that has to happen is the attacker has to try to fight them in a straight up fight (storming/assaulting rather than sieging) without having a ridiculous numbers advantage against the defender. The AI and most competent players will, of course, resort instead to sieging in this case because they aren't too stupid to live.
The point I'm making is that comparing EUIV and CK2 forts to stellaris fails because in stellaris you beat forts by assaulting them, not sieging. The reason people think they should have good odds vs. 6 battleships and the fleet that comes with them is that in CK2 and EUIV and most of earth history, in an assault they can and do win against numerically stronger enemies. (I recall a story of a garrison of 6 holding a noble's castle against an assaulting force of 80, though I can't remember the reference off the top of my head).
If paradox want forts to be a roadblock, they need better siege mechanics. That probably means keeping a system under siege (i.e. with a blockade) and that requires something like trade or something which can be blocked to impose a defense penalty and induce surrender.
But yeah the reason people dislike the current implementation of stellaris forts is that they can't be sieged, since proper siege mechanics don't exist (imaging CK2 if the only forts were the lvl 1 ones you build to hold nomad provinces), but they also don't win vs. a non-overwhelming assault force.
- 7