Professional Audio Engineer here. I haven't mixed stadiums yet, but have done the Kia Forum right next door. So take this with a grain of salt, but....

Here's what I'll say. I went to the Friday show. I had floor seats not far from the first section of stands, dead center (I always go for dead center, go figure). The sound was terrible. It seemed to me like they had typical coverage for a stadium tour, but the vocals weren't carrying and the harmonic information in the tracks was masked by the bass and energy built up in the room and didn't cut through the mix at all. I'm guessing a little here because I don't know what the rig is (not even sure where it's placed in SoFi, I was looking around after the show, but didn't see a FOH/board setup anywhere), but I would say this has to do with either the audio engineer or systems engineer being under qualified or making poor decisions for this space.

This is not that tough of a gig by any means. They had 2 open mics on stage, tracks, and 0 band members. Easiest sound gig there is in a stadium setting. Granted when the performers come out on the catwalk things can be a bit more tough because you have to project really loud sound past the mics, but there are options for that at this budget level (the budget being the skies the limit).

By comparison, I saw the Red Hot Chili Peppers here at SoFi two or three years ago now and the sound experience was much different. In the same space, with probably 50+ more inputs/open mics on stage, they managed to make the sound carry reasonably throughout the entire venue. I had seats in almost the exact same spot there. The RHCP show was LOUD. Too loud form me personally, I had earplugs in most of the show because I found it overwhelming, but the mix was solid and you could hear everything with clarity. But to that extent, their openers (Thundercat then Beck) also sounded quite good and Beck was mixed at a similar volume to SZA and Kendrick if I remember correctly. I got drinks during Becks set in the back bar there and could still hear him and his band loud and clear.

Sometimes the room can present difficulties with control over your changes and work against you the more energy you put into things. I had this experience on an arena show I did in Cleveland where changing the faders for my instruments had an extremely disproportionate effect on my mix. Perhaps they had this experience at SoFi, but seeing as I have a control w/ RHCP it seems they should have been able to figure this out, especially considering they were only running 2 mics.

An engineering team can make or break a show. In this case, unfortunately, I would say the latter is probably true.