Don't get me wrong I want a JL movie but a good one.
I don't necessarily buy that the masses of general movie goers are as fully understanding of DC characters as some allege. Of course we all want the big 6-7 but will people(and I'm saying it's more than many think) who don't really know Flash, MM or only think Aquaman is a joke buy into a film with the other 4? Minimal explanation at best, go get 'em Flash. And they may think GL is a bit of joke after it's underperformance if they saw it at all.