Complete junk. An overly long, poorly paced, badly written snooze-fest. Not a single compelling or even likable character, and every single actor acted like they were sleepwalking through their roles, probably because of bad directing from Zhao, who obviously should have kept making arthouse crap and not been allowed to try to make a real movie. That said, Richard Madden (Ikaris) was just shit, I doubt even a decent director could have helped him. He was like the British (Scottish?) version of Mark Wahlberg from The Happening, except not unintentionally funny like that performance was.
It was impressive how much the movie hates Jack Kirby and his creations, with both the entire premise and literally every character completely unrecognizable as any version of The Eternals. Its like how Zack Snyder fucked over the New Gods, except I think even he at least read a wikipedia entry on characters like Darkseid, while I'm pretty sure this movie was just the names of the Eternals slapped onto random characters in the script, with maybe one person telling the people making it things like what powers each Eternal should emphasize and things like Sprite's situation.
The movie doesn't quite piss me off as much as Ant-Man & The wasp, and didn't irritate me as much as Spider-Man Homecoming/Far From Home, so I'd put it as "only" the 4th worst MCU film, but its definitely a bad movie and not one I'd watch again. It really doesn't even need to be watched once, its basically completely irrelevant to anything else anyway (not that it would be better if it was connected, but its not even worth a begrudging hate watch as it is).
D-, and it only gets that high of a rating because of the three worse MCU films that I mentioned.