* If tomatometer & audience score are within 5% of each other, you can trust the ratings to give you a decent indiciation of movie quality.
* If tomatometer is more than 15%+ higher than audience score, it means it's an artsy fartsy movie that critics like and movies don't.
* If audience score is 15%+ higher than tomatometer, it's a fun movie even if it's not oscar worthy. (https://www.rottentomatoes.com/m/old_school is a perfect example)
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The Last Jedi
Tomatometer 91% Audience 41%: Artsy Fartsy
[Really?]
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The Greatest Showman
Tomatometer 56% Audience 86%: Fun, not oscar worthy
[Won Oscar for Best Original Song]
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EDIT: Truthfully, it was the release of these two films (both Dec 2017) that caused the Tomatormeter and I to part ways. Simply indefensible, IMO.
[0] Think space-walrus cliffs, or red-salt Hoth, or lightspeed kamikazee, or the Snoke throne room battle
While I agree with your criticisms of The Last Jedi, I don't think you can under any circumstances consider this movie "artsy fartsy".
The Last Jedi is the anti-artsy fartsy movie, otherwise the term loses all meaning. It doesn't mean "bad", and an artsy-fartsy movie can be good. Focusing on just the technical or glossy aspects doesn't make a movie artsy, it just makes it bad.
Critics love these movies, because first they see lots of movies, and something doing different, even if the different doesn't really have anything behind it, is refreshing. Also, since there isn't really any plan, you can read everything behind it, which allows you to write whatever you want very easily.
Especially for the SW universe which is getting stale, and the sequel trilogy was stale from the beginning. Euroartrash allows the illusion of a new path. An illusion, since if the movie went the way some critics imagined it, a certain character had to make the other choice at the end. But you wouldn't subvert the viewer if they had.
Viewers don't like them anywhere as much - turns out trying to confuse the viewer for the sake of it doesn't make for a good experience - and it's a bad fit for a movie universe. They really picked the wrong directors for that trilogy.