Why The World Doesn't Recognize Wonder Woman After 1984
Warning: SPOILERS ahead for Wonder Woman 1984.
Diana Prince saves the world in Wonder Woman 1984, but despite reaching out to people all over Earth, she still manages to remain anonymous. Both Wonder Woman solo movies are prequels to Diana's first appearance in Batman V Superman: Dawn of Justice, in which even master detective Bruce Wayne is unaware of her superpowers until she shows up to intervene in the final battle. Because of this, Wonder Woman 1984 had to take care to maintain Diana's secret identity, so that three decades later she can still be leading an incognito life as a museum anthropologist.
Wonder Woman 1984 opens with some low-key superhero antics, as Wonder Woman prevents a heist of valuable artifacts in a shopping mall. Before launching properly into the fight, she throws her tiara like a boomerang and knocks out the mall's security cameras so that she won't be recorded. When a little girl marvels at seeing Wonder Woman beat up the robbers, Diana raises a finger to her lips to indicate that the girl should keep her secret. Afterwards, there is widespread confusion about who intervened to stop the robbery.
This explains how Wonder Woman has been engaging in small-scale fights to save people, but viewers may be confused by the end of the movie, when she hijacks the satellite array that Max Lord has been using to reach out to everyone in the world and collect their wishes. After Diana gives a speech about how it's not up to her to save the world this time, Lord realizes that she has wrapped her Lasso of Truth around his ankle so that she is projecting her voice to the world. People obviously hear her voice, since her speech and the Lasso's power convinces everyone to renounce the wishes they made. However, they don't actually see her face.
A shot of Piccadilly Circus in London reveals one of the many screens around the world that Diana is projecting her message through, and it simply shows the bright golden glow of the Lasso of Truth, rather than Diana's face. Wonder Woman knocked out the only camera inside the satellite base, and after that the machinery was used to project the concepts that she and Maxwell Lord represented rather than their faces: first the lies and deception from the Dreamstone, and then the truth from Wonder Woman's lasso.
The general public's failure to recognize superheroes in their civilian clothes has always required some suspension of disbelief in the world of DC, as illustrated most notably by no one realizing that Clark Kent and Superman are the same person. However, Wonder Woman 1984 does a little more to show how Diana has managed to operate as a superhero without becoming famous - and the movie's post-credits scene further reveals how an Amazon can live under the radar in the human world for a very long time.