Lots of conflicting thoughts on this series so far. It's hard to get a read on how it's doing.
To my eyes, it looks like it should/will be a hit given some more time to unfold. However it seems to be racing to an endgame already at chapter 18. So either the mangaka's playing for votes to avoid cancellation, or I think we're looking at a time loop before long and this is all an extended prologue.
I hope this manages to run for a while, this series has potential I think.
For a specific point on this chapter, I think we've already touched on the crux of why the tidals are a problem and why the censors are trying to prevent full on war. Someone else may be able to expand on this but I believe the issue is with observing them. We've seen this come up a few times about how 'ignorance is bliss' and similar ideas. This invasion may all be a self-perpetuating problem. The censors observe the invaders so the invaders keep invading. Something along those lines.