They couldn't reunite June with Hannah, because Hannah features in The Testaments, living in Gilead. Yes it's really sad but like real life, people don't always get a happy ending. And I suppose it could still happen in the Testaments!
I don't feel as though she's abandoned baby Holly, she's with her grandmother who loves her. And she needs to keep fighting to get Hannah back, and to help destroy Gilead in order to make things safe for her daughters and everyones daughter.
It was so wonderful that poor old Janine got her daughter back after all her suffering, so that was like a stand-in for June and Hannah in a way.
It was good that Naomi did the right thing by relinquishing Angela/Charlotte. But to be honest, I don't think she was that attached to her really. She just wanted a child as a status symbol and seemed to leave most of the childcare to the Marthas. I remember her being very impatient with the child. Lawrence was far more loving and he'd only known Charlotte for a few months surely. He would have been a good father.
To be honest Naomi was an unpleasant woman and also not that bright. She was mean and vindictive towards the handmaids and especially Janine. She was a good match for the horrible Putnam, but Lawrence deserved better than her.