The super 8 film wasn't as much a subplot as much as it was an entry point to the grander story. The fact that the film-within-a-film's story shifts due to the circumstances around the kids is enough to support this.
Of the directors in the Amblin umbrella, Joe Dante had the sensibilities to blend his own love of genre cinema and storytelling into the narrative with Gremlins (which this film bears a strong resemblance to, along with using the same science teacher) as the prime example. Explorers isn't an Amblin flick, but the cube shooting through the wall seemed like a direct reference.
I guess the point I'm trying to make is that while Abrams models the emotional make-up of the film around Spielberg's work specifically, I found a particular inventiveness to it that puts it alongside the other Amblin flicks. Should the film be knocked for not aiming to be greater than a pastiche? Possibly. I had too much fun with what was present in the film to complain about things that it isn't trying to be.
Also, this is a perfect double feature with Attack the Block, though that film does a better job of marrying its influences into its own distinct narrative.