Spoilers should be fine here as long as they are marked. I saw it again today and I liked it just as well the second time, possibly even a little more since I already knew what the structure of the film was going to be.
But I also can more clearly explain the few areas that I felt left room for improvement. I don't go so far as to say "lackluster", but I had just a couple of cons that I wanted to talk about in more detail:
*This movie needed another "Clark Kent" scene. He was really only Clark Kent once in the entire film and it's the contrast between Clark and Supes that plays really well. To his credit Corenswet did a fantastic job as both characters, unlike Cavill who is a good Supes but an AWFUL Clark or Routh who was a very good Clark but never really had a chance to shine as Supes. The one scene he did have as Clark at the Daily Planet was really really good and his interactions with his co-workers were all solid. I'm not sure when they would have had time to squeeze in an extra Clark scene, but especially on the second watch I definitely noticed the lack of Clark screen time. Maybe they could have fit something in before he got imprisoned? But things kind of popped off after the monster fight so it could have been difficult to squeeze something in.
*I really disliked the way they portrayed Luthor's lackeys, specifically the way they showed them controlling Ultra Man's movements. I didn't really need them to give a detailed explanation of HOW they were controlling his actions (it would probably involve a handwave and something about "nanobots"), but seeing them grinning stupidly while leaning around swinging a joystick just really irked me. It's like when someone is playing video games on screen, but they don't really know how games work they just end up doing way too much movement and mashing in a completely unnatural way. It probably doesn't play as poorly to someone who doesn't play games, but there are a couple of brief shots of it that I just hate. Also they didn't really give any justification for why anyone in that room idolizes Lex to the point that they are whooping and hollering while participating in the attempted murder of Superman. I'd guess there ius supposed to be some parallel with modern day Elon worshiping Tech Bros, but a little something to justify his following would have been nice. Even if it was to establish at some point that Luthor Corp was a company with a track record of being incredibly beneficial to society? Like revolutionizing medicine and making it available to the masses? Or solving world hunger with science? Instead all we know for sure is they sold billions of dollars of munitions to a despot.
But other than that I really can't find much to fault. Despite having 3-4 other good guys it was still very much a Superman focused movie and it also didn't spend an hour ruining the pacing on an origin story. You get just enough at the very beginning (definitely don't miss the first 30 seconds of this movie, they establish a rough timeline) but then it's straight into the action.
All of the other reporters from the Daily Planet were done very well, especially Jimmy. They were useful enough without the movie becoming too much about them.
I think they picked good other heroes to include in the movie (#JusticeGang) and even though Mr. Terrific got the most time on screen, Nathan Fillion's Green Lantern is excellent and I love how much my wife hates his haircut. There was more romance in the movie than I would have assumed coming into it, but it didn't feel like it was shoehorned in or like it ran too long either. All in all I stand by my original reaction that it was a very strong showing for the new DCU.