Bojack isn't just depressed. He's almost certainly got CPTSD, possibly with a personality disorder (HPD feels right but I haven't watched since the finale was new). His life sucks because he keeps giving in to his worse instincts and desires.

Hrs very relatable as someone who struggles with CPTSD, and had to learn how to do healthy and responsible things instead of just whatever my brain says.

But fundamentally as a character he represents the failure state of managing trauma. He keeps trying and he keeps failing harder and harder, but never seeks the real help he needs or learns to have a setback without spiraling out of control and hurting someone else, usually pretty bad. Hell, he keeps thinking that dependants will make him better and then damages them because of course they won't.