like the first mission impossible full of twists with people constantly revealing they are not who they claim to be. And I disagree that it would have been hard to set it up, instead they should have looked at the gaps in previous stories, plot-holes and unanswered questions, like Who Was Sonny Burch Working For? Why Were The Sokovia Accords Repealed? What Happened to the Stolen Pym Particles? etc. The gaps in these stories can be explained by Skrulls either working for Fury or against him. It would be fun to composite shots of skrulls in the background of older movies (and save budget)
We have establish Skrulls in other projects, like Skrull Electra in Echo
Connections
We retcon skrulls helping Fury to repeal the Sekovia accords and resolve a few other unanswered MCU questions
Sonny Burch was attempting to steal Pimm Particles for the Power Broker who has also stolen tech and dna samples from the damage control clean up crews and sells the skrulls the ingredients for making a super skrull
Ironheart is making a Skrull detector for president Ross
President Ross is hinted to be Red Hulk and declares war on asgard and all aliens at the end