There are many paths to MCU canonization, but the most common is also the simplest: the cameo. It doesn’t matter if it’s Howard the Duck in Guardians of the Galaxy or Kelsey Grammer at the end of The Marvels; as long as you appear somewhere in the main MCU timeline, you’re good to go. But lots of MCU stories, like much of Loki and Deadpool & Wolverine, exist outside the main timeline. Seeing Chris Evans as Johnny Storm was cool, but calling it canonical isn’t accurate.
Now, however, the Marvel show that thumbs its nose at canon is poised to introduce two characters that will be at least somewhat canonical; one pulled from elsewhere in the Marvel universe, and another who’s brand new.
