In Wandavision, we see that Agatha Harkness possesses a copy of the Darkhold. At this point, the opportunity was lost for him to mention that there were previous bearers of the Darkhold (at that time, it was not known whether or not it was the same book from Runaways Season 3).

In She-Hulk: Attorney At Law, the events of this series are set in Los Angeles. At this point, the opportunity to include a case involving a company like Wizard (owned by the Minoru family) or NEMO (owned by Victor Stein) was missed.

In The Marvels, there were very small rumors that we would see the return of the Gibborim alien race, which was a crucial part of the Runaways series; it was even thought that we would have Virginia Gardner return as Karolina Dean, but in the end, that did not happen. At this point, the opportunity to see the Gibborim in a Marvel Studios production was lost.

In Agatha All Along, it was rumored that Aubrey Plaza would play Morgan Le Fay, a role previously portrayed by Elizabeth Hurley in Runaways Season 3. Initially, this seemed problematic as it would de-canonize the events of Runaways, but it could also have been a recast (like Don Cheadle replacing Terrence Howard). Ultimately, it turned out that Aubrey Plaza was playing Death. At this point, the opportunity for Morgan Le Fay to return in some form was lost.

In Wonder Man, we see that the series is set in Los Angeles. At this point, the opportunity was missed to mention Frank Dean, Karolina Dean's father, who is (or was) also an actor, possibly of the same caliber as Trevor Slattery.