To me, it sounds as if it is not:
“Heresy is the obstinate post-baptismal denial of some truth which must be believed with divine and Catholic faith, or it is likewise an obstinate doubt concerning the same; apostasy is the total repudiation of the Christian faith; schism is the refusal of submission to the Roman Pontiff or of communion with the members of the Church subject to him” (CCC 2089).”
Doesn’t the above exclude Islam? Or am I wrong?
You’re right.