When reviewers talk about "objective analysis", it's often strawmanned to mean "my opinion is objective and you can't disagree with it".

What it really means is that some aspects of a work can be looked at objectively and pointed to as a reason why something may or may not work.

For example, if a shot in a movie is out-of-focus, it's out-of-focus, and no amount of Reader Response Theory sophistry can change that. All you can argue about is whether or not that shot being out-of-focus is intentional, and what artistic purpose it might serve if it is.

Similarly, it's possible for a movie's plot to have objective flaws, such as events not following a logical causal chain. If no logical justification can be made, then those are objective flaws and all you can do is argue over whether or not they bothered you subjectively.

You can argue that a plot hole isn't a big deal and doesn't bother you, but that's not the same as proving it doesn't exist or isn't a flaw. It objectively exists regardless of whether or not it affects your enjoyment of the movie.

Pointing out the objectively true facts of the story forms a baseline which can be universally agreed upon so we can discuss what does or doesn't work and explain why we feel the way we do.

The One Ring needs to be brought to Mordor to be destroyed. That's an objective fact within the context of the story. Now we can argue over our subjective opinions about whether or not the journey to get it there was satisfactory.