The fuck is with the harem-haters?
Both polyamorous and monogamous relationships have their place. Just because this series is pushing the one-on-one angle isn't an excuse for everyone to start bitching about "trash harem". Both approaches can be valid if they're handled properly. Similarly, both can be completely mishandled.
I'm still waiting to see two-way collective polyamory even attempted in a manga. I think the closest I've seen is Bakarina's equal-opportunity bisexual harem (which she is still dense as fuck about so she doesn't even know it exists). But what I'm talking about is a situation where it isn't just a bunch of people all loving one individual, but a bunch of people all connected with each other the same way.