I like the series, but it had an ending that also works relatively well as a series finale. With that, I can conclude their story well. Bringing the characters back should feel important enough to revisit a completed story.
They don't connect really other then I guess time travel however for some reason there time travel logic doesn't exact fit with the canon at all. In fact Agents of SHIELD using the Quantum Realm at least showed the writers were aware of the canon. Also Agents or SHIELD and Agent Carter were the only two to feature movie characters until the Disney+ shows.
Why? I've seen the TL;DR video made by Marvel about the Runaways comic storyline and I don't know how that got adapted to the MCU but this guys has NOTHING to do with the multiverse, the TVA and Loki!
I was never the biggest fan of Runaways but they are definitely interesting an unique. Maybe getting them involved in one of the episodes, but I'm not sure about them being the forefront of one.
