I think the bojack show is about bojack, but also about Diane. If we see the show starts when Bojack meets Diane.

They are very similar in many ways. Diane and BoJack are both clearly depressed, neurotic and have family trauma.

At the beginning of the show, we see that both are always making excuses for not doing what is right.

The only difference is that Diane wants to do what's right, just because she wants to be a better person. While BoJack wants to do what's right just to feel better about himself. (In a way he's selfish and just wants self gratification fast).

We end up seeing that the intention behind the action ends up influencing, because one of them improves lives (although it's not easy). While another never changes (I'm trying not to spoil it, but it's obvious who it is who).

That's why they seem like a good romantic couple, because they have the same problems in parallel situations.

But, in the end, they have different values and in my opinion, it is necessary for people to have similar values to be a really good romantic match.