I think the reason why everyone hates the ending is that it's depressing and the characters basically just "accepted" by the characters when no reasonable AI copy of a human mind would accept being forced to be stuck in a Circus simulation.
Because there can be a storm that causes a power outage that shuts off the computer containing this simulation, if that happens. Wouldn't they just be as good as dead? Or maybe another homeless guy decides to come and just destroy it for the shits and giggles.
Yeah, I think it's reasonable to hate this ending and understand why people like PPP were pissed off about it.
Not just that, if they don't have memories of their human selves, why would they be upset being stuck in this digital circus if they have no idea what being human was like. It's probably worse that they know learn of what their real are like knowing what they are missing out on.
Logically, I think the best thing they could do is somehow hack into the system and make themselves completely forget about their former lives and their former humans selves.
They would be able to effectively gaslight themselves into thinking they were never human at all, and just think they were an AI the whole time like Caine and the other NPCs and continue living in the circus world with them with blissful ignorance.
Until their world inevitably dies when the computer breaks down for whatever reason.