While I see this being a problem, I don't really care. Stellaris is so asymmetrical game it's impossible to both keep balanced for competitive multiplayer and retain its incredible roleplaying value. If you play Stellaris as a game of conquest, then of course every empire should be militarist xenophobic hellhole. That's just the best way to play if your goal is to subjugate all others. There's little that can be done to balance it, and that's the point: it's not some competitive e-sport. If it's played like that, you have to abandon large portion of mechanics because they aren't optimal for military conquest.
Anyways, what happens after this strategy is so widely known everyone uses it? Imagine attacking someone with your corvettes and finding out they've been doing the exactly same thing? I mean, it seems everyone should do this strategy if they're playing in a multiplayer game where goal is to kill everyone else.
I don't really care much, since I never play multiplayer games like that. Stellaris is just better to be played in a more sandbox way where victory is not win condition, but having fun experience for everyone. A bit more like dev clashes.