Sometimes what you don't say, is just as meaningful as what you do. Fans of Marvel's Agent Carter are not thrilled to realize that when the character, who first appeared in Captain America: The First Avenger and is set to appear soon in Marvel's What If...?, got herself an episode of Marvel's Legends, no clips from her solo series were anywhere to be seen. After the success of her role in the Captain America movies, Hayley Atwell took Peggy Carter to the small screen in Agent Carter. Years after its cancellation, a vocal segment of fans still want more of it...but Marvel, it seems is going completely the other way.
Just like they seem to have done with Marvel's Agents of SHIELD, it looks like Marvel Studios will be discarding the stories told in Agent Carter. The Marvel's Legends episode focused exclusively on Carter's appearances in the MCU's feature films (and the Marvel One-Shot special attached to one of the movie Blu-rays).
While they aren't promoting it, Marvel's decision to ignore any TV that was produced before Kevin Feige took control of Marvel's television arm has been evident for a while. This "clean slate' approach has already removed Marvel's Agents of SHIELD from canon, with some rumors suggesting that Marvel has designs on characters like Quake and Ghost Rider, who appeared prominently in that show.
The intent seems to be to suggest that while the shows still "happened," they didn't happen in the main world that the Marvel movies and TV shows focus on. Those stories took place elsewhere in the multiverse. It's too bad those rules weren't established when the shows were on the air, and could have benefited from the freedom you get when you're unshackled from that wider continuity.
It seemed to many that Agent Carter, since it took place in the time between World War II and the first Iron Man movie, might still "count" since it was unlikely that it would conflict with anything Marvel might want to establish later. With projects like The Eternals, though, it's possible that Marvel just doesn't want any unexpected bumps in the road when exploring the universe in flashback.
Marvel's Legends is a recap-style series that is intended to get audiences up to speed on a character's MCU history, ahead of a new project featuring that character. Virtually every lead in a Marvel Disney+ show has had one, from Wanda and Vision to Loki and The Falcon. Even Sharon Carter, Peggy's niece who has had a fairly minor role in the larger MCU, got an episode.
In an ironic twist, some fans have pointed out that the thumbnail image for Peggy's episode of Marvel's Legends...is actually a promotional image from Agent Carter, featuring her familiar red hat, which never appeared onscreen in the Marvel movies.