This is a long long way from the BoJack horseman we saw in season 1. Haunted, broken, continually failing, always making excuses and always blaming everyone else, always hurting others but not knowing why. Beating himself up constantly for his own mistakes, and then drowning those mistakes in yet more mistakes.
I think since his mother is now dead, the only person he has left to blame for his mess-ups is himself.
The writing in this show is absolutely fantastic. It's always been good, it's so good that it allows you to see through the ridiculous human-animal hybrid world that makes no sense at all, and look only at the personalities and their behaviours and interactions.
The writing continues to be the biggest strength it has, and it is seen in not only what the narrative tackles here, but the way it does it while doing other things too. It deals seriously with the main character in a convincing downward spiral, and another character seeking a baby to fill a hole in her life, but at the same time having space for a crudely-constructed sex robot to become the CEO of a company which tells you the time now, and having Todd in a 'swapped identities' sexual farce with a family of axolotls. As before, the show does this with neither element detracting from the other. It also continues to push for new ideas and risk-taking; the episode-long monologue being the most famous example, but it is hard not to enjoy and admire the reality blurring penultimate episode for how well it relays BoJack's breakdown in a way that can be understood.
The animation and voice work continue to be top notch, but it is the dept and creativity of the writing that makes this show and this season so great - from the continued character depth, the background gags, the creativity of presentation, and the way it all comes together as a whole.
I suppose an argument could be made that the show has always had dark elements, but mostly what I remember from previous seasons was clever industry insider jokes and tongue-in-cheek social commentary similar to 'Arrested Development' or 'Community'. The risk, I think, is that at a certain point the drama can overpower and wash out the humor, and I think this episode came really close to that.
Also, even though this is a cartoon, depicting the main character doing things that are really ugly and disturbing might make it difficult to empathize with him again in the future, even with the explanation offered for his actions. The bottom line is that I didn't hate this episode or the overall arc, but I'm a little worried about whether they can tie it off without making the show kind of a bummer or creating some serious cognitive dissonance as they try to get back to the funny side of things.