“Captain America: Brave New World” is losing momentum at the box office, even during a muted winter weekend with hardly any competition.

After a strong $100 million start over the extended Presidents Day holiday frame, Disney and Marvel’s “Captain America: Brave New World” crumbed by 68% in its second weekend with $28.3 million from 4,105 North American theaters. The Anthony Mackie-led superhero adventure, which remained in first place on box office charts, has generated $141 million domestically and $289.4 worldwide to date. “Captain America” cost north of $180 million before marketing, making the production budget slightly less expensive than other Marvel tentpoles.

It’s not uncommon for comic book tentpoles on the scale of “Captain America” to significantly slide in subsequent weekends. Yet this film, saddled with negative reviews and poor word-of-mouth, fell on the steeper side with a drop closer to 2023’s “Ant-Man and the Wasp Quantumania” (down 70% after a $106 million debut) than “Guardians of the Galaxy Vol. 3...