You're right. It isn't, because the same shit has been happening to Sansa since season one. And Ramsey's been doing the same shit since he's been introduced.
That's part of the problem.
Rape is still very much shocking to see, and rape of a character we've practically seen growing up is shocking, too. It's still shock value. It's just bad, because it's the same shit we've been seeing. No one's arc has changed in too long.
Sansa being married and being forced to act like an adult in a hostile environment with a husband that was chosen for her and demands sex the way Dany and Cersei were, is actually a big change.
Reek being tortured by bad things happening to someone else instead of himself is a change. If you accept the premise that him remaining as Reek so long is partly because he thinks he deserves to be punished for all he did wrong, then you can see how Ramsey may have finally pushed him too far.