I actually think this is a great, thoughtful question.
A lot of people even in this sub will just say “Bojack is a bad person” and I think they are missing the entire point of the show.
Bojack is dealing trauma. The trauma is generational and deeply affects his daily life. We get glimpses into his mind throughout the show and it is not pretty. The “stupid piece of shit” monologue is only one episode but the show makes it clear that that’s how his brain works all the time.
Almost every bad thing Bojack does is in search of relief from that negative, awful chatter. He just constantly does so in bad ways. Namely through drugs and alcohol. And mixing that all together makes for some extremely bad decision making. I think Bojack’s self loathing also “gives him permission” to do bad things, and sometimes I think he does bad things because he hates himself and thinks “this is what a shitty person would do.”
The show’s greatest achievement imo is presenting all of this and showing Bojack as a character in pain and as a vulnerable human, but also making it extremely clear that this does not make it okay that he does what he does. He’s not given permission or even necessarily forgiven. It can be understood but not condoned. He is a victim in many ways and hurt people hurt people, but it doesn’t give him the right or make it okay to be shitty. He still has to do better.
It’s objectively worse ending from the point of view of the show. What the show sets up, the themes it introduces and hammers over and over. Death is cheap and easy. Living is complex and nuanced. That’s what the show is.
If Bojack dies we weaken the themes of redemption, consequences and accountability, continued struggle, and hope.
If you want to believe he died, sure. But literally it isn’t what happened in the show (as we very clearly see) and it would be a worse ending. So I’m not sure why you would choose to decide for yourself that what you saw with your own eyes wasn’t real, and invent a worse ending overall