You'll find that many if not most traditional Catholics reject Faustina and her false mercy. The novus ordo folks really like Faustina, because they believe that they get the mercy without repentance, and going to confession is not something the novus ordo crowd likes to do.
The irony (especially because I think it has one of the best pieces for confession I have read). I know why many traditionalists reject it, guilty by association, which is why I would need a new thread to discuss it all, these are mostly just character assassinations instead of refuting what I said and thus not serious discussions, furthermore, I can tell whether someone is being honest or not by the criticism they use, as I know what's fabricated and what's not.
Furthermore, it's private revelation so one doesn't have to believe it, some day it'll be an interesting discussion to have and even if you still disagree you will at least understand it, but others bringing it up here is mostly just for character assassination IMO.
There are two things I have read regarding St Faustina's diary that have shaken me before... but there is something else that has greatly reaffirmed me, so there is some legitimate criticism, but I am certainly sure enough and there is a whole bunch of just bogus criticism.
God Bless