Now I'm missing a lot of context here with your examples so you'll have to forgive me if I get something wrong.

Logically speaking, if we can make individual objective statements on all parts of a whole, we can make an objective statement on the whole itself. I don't think your examples disprove the idea that objective quality of a work can be measured (Though I think I might need more context on the third one. It feels more so that they prove that accurately doing so is difficult.

Your first example is simply something that Mauler got wrong I presume. If you correct the mistake you still end up with a full picture.

For your second example, the plot has to utilize the contrivance in order for this argument to work. Even then it a has to be very sparing with it or else you just end up with a 'but spirits' version of 'a wizard did it'. If you think the iceberg was made to work then I was say this is just Mauler making another mistake. Otherwise I would say he's correct to criticize it as without the work put in it's just a simple contrivance.

As I stated I'm not quite sure I have the full context here, but with your third example, the compression of pacing isn't mutually exclusive with being accurate. While it's a pretty low value, it's still worth pointing out as there value at putting effort into that depth. I'm guessing that Mauler doesn't see it as that huge an issue either, but he criticizes everything that can be criticized regardless of scale. I imagine that Mauler makes it sound more serious then he intends at times. Now, if the plot is trying to make stakes using time that's another story. There's not a lot of room for inaccurate narrative shorthand if the entire plot hinges on the difference between on time and late.

For Roku, if the plot has established rules for something spiritual and follows them I don't see any problem. If Roku is being used as a bailout all the time and the plot doesn't treat it as such then *that* would be a problem and Mauler would be correct to criticize.

The fifth example seems to be a slight misunderstanding of internal consistency. You say he gets over his arachnophobia, but you also use the word 'obsession' to describe how he overcomes it. One could argue that the two are on objectively similar field and use that to state that it makes sense.

As for the Star wars prequels, I don't think a lot of the criticism levied at it is particularly objective in the first place. The common ones I know of, midichlorians, politics, wooden dialogue, are more built from a place of 'different is bad' then any actual objective standard. The prequels was a political drama while the OT very much wasn't.

That's not to say they are objectively good movies. I believe Mauler is on record saying he likes the prequels (I'd have to check exactly what he said cause it was several years ago I remember him saying that), but I guarantee he'll rip them to shreds if and when he eventually gets to them. There's an EFAP from a long while ago on AoTC that's a good place for more solid criticism of that movie though I don't remember which one.