I think marketing. The film releasing all of sudden in December was surprise. I still can't believe WB is dumping it like this. Usually you have cast of film doing rounds of interviews and promotional events.
When the first trailer came, it was red hot but that was so long ago. After that all the promos were basically footage from first trailer. So there wasn't any reignition in the buzz.
Other reason I would like to believe though could be just something I think, in MCU you want to watch every film because something happens in every film. If not general audience, after 10 years there's a big enough 100mn plus hard core fans across world who are keeping up with what's happening and then there are millions of casual fans. WW84 felt like a standalone film. DCEU is going nowhere. So there wasn't any thrill as such.
To top all these, the film is coming in free next week. It will be interesting to see how the traffic of film outside America is next week after its HBO Max release, when it hit piracy platform. I think China social media will be best judge of it.