Unscientific does that job already, while the '-ism' suffix denotes, in this case, belief in science. Why let them have a perfectly good word?
I think "scientism," "unscientific," and "pseudoscientific" all have different and necessary meanings: respectively, "attempting to use scientific epistemology but misunderstanding it", "using bad epistemology," and "using bad epistemology but making a deliberate effort to look like one is being scientific". The word closest to meaning what you want "scientism" to mean is probably "Bayesianism".
Here's the new thread for posting quotes, with the usual rules: