The reviews are mediocre, and the film cost so much that it's been called a box office bomb because it "only" made $29 million on its first weekend (the top box office draw, but that's not enough). I'm not sure what the problem is. It's not as good as Terminator 2: Judgment Day, but then, T2 wasn't as good as The Terminator, which remains the only classic of the bunch. I guess people have expectations.
You might say Tim Miller is up against another Miller, George, of Mad Max fame. Thirty years after the heyday of Mad Max movies, George Miller made Mad Max: Fury Road, which is not only the best film in the series, but the best movie period over the last decade. Just as Dark Fate isn't as good as the first two Terminator movies, it's no match for Fury Road. But honestly, so what?
Mackenzie Davis kicks ass at the beginning of the movie, and I am a big fan of hers since Halt and Catch Fire, so maybe I'm easily pleased. Much is made of the return of Linda Hamilton, and she is great, but for me, Davis is the highlight. The rest of the movie? Well, there are some good action sequences, it's fun to see Hamilton and Arnold together again, and if the plot is confusing, what the heck. If you don't come in expecting a return to the original (or the equal of Fury Road), you'll enjoy Dark Fate. It's no classic, but I bet in ten years, people will wonder why Dark Fate got a bad reputation.