One of the most unforgivable elements of this is it was a spy movie without much spy shit.  
Act 1 establishes a bunch of operatives, each with their own specialty.  You have a shapeshifter, a honeypot, a nano-alien who can get inside tech and disrupt it, and a big dumb guy who serves as a heavy.  Along with a head guy who doesn't do much other than glower and punch hard, and a Starfleet minder who has no clear role.  
The characters with the strongest established skills have zero payoff.  The honeypot tries to use her skills on a single character for half a second before she gets vaporized.  The big dumb guy crashes through walls, and kills no one.  The shapeshifter only shapeshifts for gags, and never uses his skill for anything plot-related.  And the guy who can hack tech does do it, but only for the bad guy.  The two characters with the most boring/ill-defined skillset survive to the end of the movie.  The best we get to see them use their skills is in a theoretical montage of how they plan for an heist to go down, which Georgiou scuttles for something far, far more boring and direct.  
And that's Act 1.  Act 2 is not spy shit, since it's just the motley crew trying to figure out who is the traitor.  And Act 3 isn't spy shit, because what the characters end up doing (teching the tech, and punching bad guys hard) is the exact same stuff you could see in any action-focused episode of Star Trek.
Though very different, in some ways it reminds me of the critical failure of Marvel's Secret Invasion - another supposedly espionage-related project which completely forgot what makes paranoid spy thrillers fun.