I suspect most don't have any problem with knowledge that is true and profitable and worthy of knowing. It is "Gnosis" in the sense of heresies and baiting unto error that is the stuff of what many seem to dislike about "religion" which isn't in the Bible to begin with. Salvation is through faith/believing. However it is also written that: "Faith without works is dead". Much if not all of the burdensome doctrines or ideologies that came to be associated with the Bible or "Christianity" seem to have come from the "Gnostics".
Divine knowledge and wisdom continues to be available to and helpful the believer of course. Knowledge isn't the problem. But not all "knowledge" is profitable. Not all doctrines are sound.
The primary type of Gnostics being referred to are the types that felt that people had to be part of a secret clique in order to "approach the Divine" or had to join a secret society in order to have "true knowledge". The Nicolaitans were said to be of the Gnostics.