I just saw this, but, to be honest Firefly is at least as funny as Guardians.
I understand the point you're making that there's a certain winning formula and Guardians just had it, but I don't think it's as simple as you're making out. Firefly was pretty charming, and it's still very much beloved, it just didn't set the world on fire at the time. Guardians had the benefit of a marketing department, so did Deadpool, also they' probably captured the interest of a younger audience who understand self-reflexivity in ways 90s kid didn't really, while simultaneously giving older generations nostalgia and genre tropes.
Back to Cloak and Dagger; I think it looks fine - maybe a little non-descript; but, I'm also fully aware that the targeted audience is definitely not anyone on this board. We have a thread called "Grumpy Old Men", not "I'm a millenial and I live in the zeitgeist".