The core question of ethics as posed by the ancient Greeks is something like "what is the best way to lead your life".

"... to accomplish what?", is a damn reasonable follow-up, and ends (telos) is something the same Greeks discussed quite extensively.

Modern treatments have tried to skip over this discussion, and derive moral arguments not based on an explicit ends. Problem being they still smuggle in varying choices of ultimate ends in these arguments, without clearly spelling them out, opting to hand-wave about preferences instead.

As such this question is often glossed over in modern ethical discussion, and disagreements about moral ends is the crux of what leads to differing conclusions about what is ethical.

Is it to maximized your own happiness like Aristotle would argue, or the prosperity of the state, or the salvation of the soul, or to maximize honor, or to minimize suffering, or to minimize injustice, or to elevate the soul, or to maximize shareholder value, or to make the as world beautiful as possible, or something else?

If you fundamentally disagree about what our goal should be, you're very unlikely to agree on the means to accomplish the goal.