They HAVE to make it less dark in order to not kill the series.
I am not talking about bringing Pyrrha back or anything but because last time they left off the bad guys won and the only reason it wasnt worse was because silver eyes Deus'ed Kevin into lawn gnome status.
In order for the series to continue and not end on Rocks fall everyone dies they HAVE to make the series lighter. Attack on titan is a craptastic world but it gives large shards of hope to the audience that things are getting better. Or at least its not hopeless.
RWBY Cinder is a giant mystery what she wants and her goals are not clearly defined. Salem is an even bigger mystery since while Qrow hints that Oz and Co are aware of her the rest of the cast are not.
So for the series to have a hope of continuing there needs to be hero wins.
I am also of the opinion that Miles and Kerry werent expecting the backlash they got. Which suggests to me they dont see the ending of Vol 3 as Grimdark or they have enough insider info they know its not grimdark.
Considering I dont think Pyrrha is dead I am leaning towards the latter. That the things we see as going too far they dont because they know what is really going on.
Its kind of like 21 where reds are negative Blacks are positive aces are ones. You have a Queen of Clubs and a 10 of Spades plus a face down card. The combo of cards you have is over 21 since a queen is 12 so plus 10 is 22. For many this is the vol 3 Finale one or the other by itself would be fine and have impact of varying degrees but the 2 together is too much.
But there is that Face down card which represents all the odd things in the Finale such as Pyrrha Ozpin and so on.
Kerry and Miles are sitting on that Face down Card HARD waiting for the right moment to flip it and show if they truly did go over or if they had an Ace of Hearts this whole time and hit 21 perfectly.
And I think they have that Ace which they are going to flip in vol 4. They are too quiet about several subjects and have flat out said watch the show to find out. Considering they say vol 4 wont be as dark just more serious and they havent responded to the backlash in any shape or fashion despite being in touch with the fans is odd unless they feel the backlash will sort itself out as the story progresses.
And before someone says well maybe the backlash itsnt as bad as you think. Take a look at Twitter Tumblr DeviantArt and Fanfiction there is some serious backlash on vol 3 finale.
Miles in fact had to make an official post that RT is not responsible for the subtitles because they were getting so much flak over them because someone thought they would be funny.
There is Backlash.