Monogamous relationships are hard. I expect romantic groups are far harder.
This is very true. Even with parallel polyamorous relationships, relationship difficulty is turned up to high. When you introduce polycules to the mix with triads, quads, or more people it takes that Duffy and ramps it up tenfold.
A triad, for example, isn’t just a relationship with 3 people. It’s 4 different relationships that have to be managed (AB, AC, BC, and ABC, are all distinctive relationships with unique needs). A quad, is 7 relationships. Going up to 5 people is something like 22 relationships to manage. So group relationships like this are pretty rare, even in the polyam world.