I’m starting to wonder if you’re arguing in good faith. No one serious is complaining about Chinacos in the early-mid game. It’s all about the late game and most of what you do is deflect with what are essentially red herrings about the early game (which I think you know that no one is talking about).
When I respond to your criticism of a fairly well-thought out list of treaty nerfs that would have limited impact on 1v1 here, you don’t respond.
Fully upgraded Chinacos are the strongest 2pop mass-producible heavy cavalry in the game. And that would be fine if they didn’t have a solidly top-three skirm, and a full (or over full) European eco on 85 pop. That’s not even mentioning an extra ~35-40 pop worth of natives (still talking about late game here).
Chinacos do the job of Hussars far better late game. They’re a little less tanky, but that’s fine (for them) because they’re doing close to double the damage vs infantry (which is the main unit type in Treaty because they are actually pop efficient). Vs most civs in Treaty, a unit that forces your opponent to build Dragoons is a massive win even before the engagement.
Other civs do, in fact, get great units late game. Some might even get three top-of-the-line units, but that’s usually paired with a roughly average eco that uses 99 pop and no unlimitedly retrainable 0 pop natives (and Conqs are one of the best in the game).