I saw this today. I expected to absolutely hate it. I'd seen all the recent clips and cameos and end credit sequences online because I didn't care at all.
I actually enjoyed it for the most part. Similar to how I enjoy Aquaman, there's enough good in it for me to enjoy it. Not what I wanted but not unwatchable.
The action scene at the start. Batfleck was good, Barry's part was poor. Batfleck in costume stood talking was absolutely terrible. He's not even wearing boots, it's like a onesie! Poor Josstice League style humor.
Keaton was better than I thought. The "I'm Batman" and "Nuts" lines don't work, at all. His score kicks in from time to time. Was great to hear but somewhat jarring too. His action scenes were decent. Not possible but decent enough to watch. Nothing comes even slightly close to the BvS warehouse scene. The stuntman looked good in the suit, Keaton did not.
Supergirl was fine.
The speed force worked in some ways but not in others.
The score was very generic. The FX were shocking at times. Surprisingly so.
Ezra's personal life aside he acting his ass off in this movie. Bloody excellent!
The humor should have been turned down 10-15%. Some of the humor reminded me of ZSJL. Laugh out loud funny but not too cheesy. There were times when it went full cheese and it would have been much better without it. Some of the lines and scenes in the trailers that I wasn't expecting to work actually did. Context is everything.
The 3rd act wasn't as good as the first two but it wasn't bad.
It's not Snyderverse although it definitely tries to be canon to Zack's movies but drops the ball too often with details that don't really fit.
I was expecting a 2/10 but probably ended up with a 6/10. Small edits here and there could improve that, maybe.