I'll admit, I was in that camp. Not because I thought it LOOKED bad, but when they announced the Labor Day weekend date I was thinking only with my box office mind and thought "Marvel just miiiiight be dumping this".
So I'm definitely eating crow now. I still don't think releasing tentpoles on Labor Day weekend will become a habit for studios. We have to remember that Marvel is bulletproof at the box office so it's going to attract moviegoers any day of the year. Most studios probably couldn't get away with this.
OR....
I'm entirely wrong and studios are learning a lesson that it doesn't matter where on the calendar you release a film, if audiences want to see it they'll show up. Let's look at the month of February. In recent years it's become a more viable month for blockbusters after being a dead zone (along with January) for so long. First you had FIFTY SHADES OF GREY breaking out to $85M+ opening weekend in 2015, next year DEADPOOL set another February record with $132M+, then of course in 2018 we saw BLACK PANTHER blow up with $202M! Presidents' Day weekend specifically is becoming a coveted slot (I hope DOCTOR STRANGE: IN THE MULTIVERSE OF MADNESS moves up to that spot next year, and the next ANT-MAN is already slotted there in 2023).
Heck, September itself has revealed its viability even before SHANG-CHI when Warner Bros. released IT the weekend after Labor Day weekend, which has historically been an even worse slot than Labor Day weekend itself. IT blew up for a $123M opening and ever since WB has used that post LD weekend date for their horror tentpoles (THE NUN in 2018, IT CHAPTER 2 in 2019 and THE CONJURING: THE DEVIL MADE ME DO IT was originally slated for September 11 in 2020).
I won't bore you guys but I guess the point is, studios are testing traditional box office dead zones and they're getting rewarded for it when they release the right films there.