Denialism = unscientific instead of pseudoscience. Pseudescience =

(1) it is not scientific, and
(2) its major proponents try to create the impression that it is scientific.

Without (2) it can't be pseudoscience.

Only if someone denies theory XYZ because of ABC and claims ABC is scientific while ABC is unscientific, only then Denialism = pseudoscience.

So outright denying XYZ is a science is unscientific but not pseudoscience. Denying XYZ is a science on religious grounds is unscientific, but not pseudoscience.