Leftism, liberalism, new Christianity, Islam are all Gnostic beliefs, ie trying to remove all flesh desires.
While those are evil, I wouldn’t call them Gnostic.
Gnostic religions are those that say you need to learn certain secrets to rise higher in “esteem”
So, the “Church” of Scientology is definitely a Gnostic type religion (though having nothing related to Christianity). I would say that Mormonism and Jehovah’s witnesses are also Gnostic, actually more “Gnostic”