Honestly, I think people put too much stock in "the brand." People don't see DC as a unified brand the way they do Marvel, hence them having a big hit Wonder Woman movie and a billion dollar hit in Aquaman, followed by disappointments, followed by another billion dollar hit with Joker, and a successful Batflick followed by disappointments. People will go to DC movies if they look good, plain and simple. Aquaman looked really fun. Joker had good trailers, The Batman looked damn good. Black Adam and Shazam 2 did not.
And while I know a bunch of DC fans thought The Flash looked good, I think a bunch of the GA (along with plenty of people on this board including myself) felt differently. When 80% of your trailer is CGI that looks bad as this does, that's gonna turn off A LOT of people. It may well be a great movie, but the trailers didn't do it justice, if that's the case. I think it will do well. It has enough hooks for that. Well enough to make a profit with that budget? Remains to be seen. But I don't think it was ever poised to be any kind of billion dollar megahit.