It's the UI that the largest proportion of your target audience would find intuitive if they tried it.
So it's not the lack of an objective answer that's the problem, it's the difficulty of finding a proxy for your target audience and a testing process you can afford.
Sometimes the proxy is "you" and the testing is "your experience and intuition" and sometimes the proxy is a statistically significant number of formal user tests.
If we're talking about UI/UX then there kinda is.
It's the UI that the largest proportion of your target audience would find intuitive if they tried it.
So it's not the lack of an objective answer that's the problem, it's the difficulty of finding a proxy for your target audience and a testing process you can afford.
Sometimes the proxy is "you" and the testing is "your experience and intuition" and sometimes the proxy is a statistically significant number of formal user tests.