You might, but to do so based solely on those metrics is a mistake. That's because those metrics don't fully capture what makes a UI efficient for human use. Other things, like cognitive load, are more important.
Does it matter if it only takes two clicks to do a thing if that usage path isn't one that meshes with the way I think? I think not, because it means that I'll spend additional time thinking about how to accomplish the task rather than just accomplishing it.
> and even worse, prioritizing "fancy" animations as if that's a good thing and as if that's your main job.
I 100% agree with you there! Animations are commonly misused and dramatically overused, and I think that more UIs would be improved by omitting them.
> The goal of UI is to optimize efficiency across most use cases (and hence users) as measurably possible.
If we're talking about "efficiency" in terms of "minimizing the use of the mouse", then I disagree. If we're talking about "efficiency" in terms of what helps a person to accomplish a task in the best way possible, then I agree -- but focusing mostly on those metrics excludes so much other important stuff as to give a distorted picture of the situation.