I think the biggest problem with polygamy based in religion, or at least in the FLDS faith, is that the husband is expected to have and procreate with as many wives as he feels "called" to have--or, in the FLDS enclave previously led by Warren Jeffs, as many wives as the "prophet" tells each man he has to have. The husbands have at least two wives, usually more, and is able to get emotional support, attention, and in theory love from each of them.
Meanwhile, the wives aren't allowed to have any other partner (I vaguely remember once on Sister Wives, the first wife Meri asked Kody how he would feel if she had other husbands, and he said the idea was disgusting and repulsive), and they're usually each raising several children. In theory they have each other to lean on, but as with any metamour situation, personality clashes and jealousy can interfere with any "sisterhood" the wives might have. One of the wives on Sister Wives has expressed that she feels like she doesn't fit in at all with the other wives and feels pretty isolated within the family; meanwhile, she only has her husband around once every four days, so there's little if any emotional support from him.
I think Kody does his best, but even though he's been married to his fourth wife for several years now (I think they married in 2010), there is still obvious favoritism there, whether or not it's due to NRE. And he's spreading himself among four wives and...18 children? 17 at least. So there's only so much time and attention he has available to give.
On the plus side, though, he does try. And unlike the FLDS enclave, where women are expected to always "keep sweet", meaning they aren't allowed to express ANY negative emotions or thoughts, Kody encourages his wives to speak their minds. The Browns are FLDS, but they and the members of the church they belonged to in Utah have distanced themselves from the Jeffs sect, and they live far more modernly and with far more equality among Kody and his wives than that sect would permit.
Can you tell I watch way too much of this show? (Or at least I used to... we don't have cable anymore, and I don't think it's available on the streaming services we subscribe to.)