Hong Chau's character of annoying. She had an annoying voice and accent that sounded like a un-pc stereotype. I think the intent was for her to sound like a stereotype and then as her character develops the audience would see her differently. Worse, her character development was based on exposition.
Christoph Waltz played Christoph Waltz.
Matt Damon's character was an annoying idiot. More than once I wished someone would slap him. Or that the movie be shown in Slap-O-Vision where anytime Matt Damon is speaking a guy in a mascot outfit with a gigantic Matt Damon foam head would walk down the theater aisles allowing viewers to slap him.
|mock up of Slap-O-Vision giant foam head of Matt Damon
At one point it is announced that Matt Damon's character is going to Norway. Why I wondered. Did I miss something? Ah, because the writer said "Lo, so it has been written, so it shall be done" Upon occasion it was preachy in a quite unsubtle way. I did like his character being a goofy idiot when it comes to celebrities. The intended direction of his character arc was obvious but not convincing.
Generally, I don't like Matt Damon. I'm not sure exactly why as I liked the Jason Bourne movies and some others but in others I simply find him grating – I'd suggest he has a powerful anti-charisma. In the Martian (2015), I kept hoping he would run out of air but despite that it was still a good movie. I laughed when he appeared in Thor Ragnarok (2017) opposite Sam Neil and Liam Hemsworth. I think my antipathy started when he was promoting Good Will Hunting (1997, awful) he went on Charlie Rose along with Robin Williams and it turned out Robin Williams was the sophisticated intellectual and Matt Damon was a window licking moron who clearly had no idea that he was a window licking moron.
Keeping that dislike in mind I can confidently say that Downsizing would have been awful even if it had been Matt Damon-less. It started out ok. The first half hour introduced the characters and the shrinking premise and not long after the special effects gimmick was introduced they basically ignored it.
The movie is described as :
"Feeling that their lives are out of control, a husband and wife decide to be reduced to tiny size to make life more affordable and leave a smaller carbon footprint. Unfortunately, after he undergoes the procedure, his spouse backs out."It sounds interesting. It wasn't. The interaction between normal sized and tiny sized were few and after about a third of the movie there were only a few oversized props to remind you what the movie was supposed to be about. Once he is shrunk his wife makes a one minute 45 second appearance (by a phone call!) and then completely disappears from the movie. It was almost as if a different movie that had nothing to do with shrinking had been grafted onto the final 2/3 of the movie.
I suspect they didn't know what to do with the premise so they opted to make it an "issue" movie so they'll get plenty of good imdb reviews because the issue resonates with those reviewers and not because of the quality of the movie.