I was one of Spiderverse over-predictors so now I'll take a more cautious approach. I think we should take demo breakdown into consideration when trying to gauge legs because WOM doesn't work in a vacuum. It's very much tied to demos. For example, Spiderverse OW audience skewed way too male, white and older than 25. So a family with small children will not value a movie recommendation from a nerdy bachelor the same way they value recommendation from another family with small children.
Spiderverse didn't attract families, women, African American audience, teenagers. Mary Poppins Returns will play well with families and women so I don't know how many of them will skip it in order to catch up with Spiderverse because reviews and single men say it's the best nerd comic book movie ever. Moreover, Aquaman is bound to be a classic 4 quadrant so men, women, families, minorities, teenagers. Again, how many will skip it in order to check out an animated version of the hero who has live action franchise, especially in the wake of another live action superhero opening? I can't speak for African American audience but maybe an African American hero whose idol is white and who is continuing that white idol's legacy including flirting with the white idol's white girlfriend from AU, is not exactly a hero that represents them? At least girls aren't represented by Gwen unlike BP where girls are plenty represented by Okoye, Shuri, Nakia, Dora Miljae, the Queen. I don't know. can't speak for this audience but I can see why BP was way better representation.
Finally, the movie opened in under 4000 theaters and had under 10K PTA. That's not hot. Many 4000+ theater openers, manage at least north of 12K (Bohemian Rhapsody, for example). I may be wrong but I thought that there's some correlation between PTA and legs. maybe not. Like, PTA isn't terrible or anything and it may go up with actuals, just that it isn't fantastic especially since lower theater count should result in higher PTA.