Well I'd rather that they only loosely reference anything from Snyder's films if they must do so at all, I don't mind them playing liberally with continuity anyway it's more fun that way imo. The biggest in universe impact from Man of Steel is the threat of global alien invasion, not the emergence of the first superhero. Snyder's stuff is way too confining for me. His Flash goes from being a novice to hitting light speed and breaking the time barrier in a single movie. Snyder's JL 2/3 would have made Cyborg into a tech god and Flash unlocking his true potential and being everywhere at once always, I mean where's the room for conflict or growth!
As for the JSA, just because you don't care about them doesn't mean others don't or won't. You can't say that they're a waste of time for no real value without having seen what purpose they serve in the movie yet.