The way to do Borg episodes is the way The Walking Dead
handles zombies. No personalization, no queens, no nuthin. The story is about the people. The Borg/zombies exist to serve only as the boogieman, to show us what the people are/aren't made of.
I don't know why Star Trek
couldn't do a Borg episode every so often without destroying them if there's a whole series about nothing but zombies, zombies and more zombies, no Klingons or Cardassians to relieve the monotony, and it works just fine. But doing zombies/Borg right does mean that everything gets tossed onto the shoulders of the human characters, and how well or not so well the writers are able to write straightforward human drama.
That's probably the problem: zombies/Borg give bad writers nowhere to hide. No gimmicks, no technobabble saves, just the merciless glare of humanity under a microscope.