The Catholic Church does not teach grace alone when it comes to salvation.

Catholics who claim that we are saved by grace alone are simply using the same illogical formulary that Protestants use when they say that:

We are saved by faith alone but the faith by which we are saved is not alone.

That is self contradicting whether you use the word faith or grace.  And two contradicting statements can not be true at the same time.

Now they want to claim that we cooperate with grace alone.  And they call that the Catholic doctrine of grace alone.  It is false.

Yes, it is true that ALL IS GRACE.   Because God caused everything by His grace.  But the Catholic Church has always made a distinction between Creation (Monergism) and Salvation (Synergism).  It is most clearly explained by St. Augustine.

1847 "God created us without us: but he did not will to save us without us." To receive his mercy, we must admit our faults. "If we say we have no sin, we deceive ourselves, and the truth is not in us. If we confess our sins, he is faithful and just, and will forgive our sins and cleanse us from all unrighteousness."

The Catholic Church does not teach monergism when it comes to salvation.  The Catholic Church does not teach grace alone when it comes to salvation.