You're missing the forest for the trees.
The manga isn't strictly about cosplay, it's about the relationship between people using cosplay as a medium. And those relationships include romance.
And people aren't upset about the cosplay being a focus, they are upset about the absolute glacial pace...
And so it ends, not with a bang, but with a whimper.
The nun arc really was the death knell of the series.
Shame, it was one of my absolute favorites before even the anime aired.
Clark was doing it on purpose for years though, and even that stretches believability. He also switches between demigod and human, so it can be excused that you don't think a mild manered dude is actually a superhero.
Here, the MC is just faceblind, and doesn't recognize his own girlfriend...