It is my opinion that Gnosticism and traditional Christianity are incompatible by definition. Traditional Christianity believes in one true God, while Gnosticism does not truly acknowledge the existence or non-existence of any one God. These two beliefs are incompatible because they are too fundamentally different in both theory and in practice.
Gnosticism is incompatible with traditional Christianity by design, hence its name. Gnostic Christianity promotes things contrary and alien to traditional Christianity, hence the long history of conflict between the two groups and even within the history of the Bible itself. Nowadays perhaps there can be some reconciliation but not totally in theology.
Traditional Christianity evolved as a religion for the masses, while Gnosticism was an esoteric philosophical branch that dealt with the Christian mysteries. So the Gnostic philosophy actually sheds light on some of the basic tenets of the classic Christian faith and should be explored for the nuances it imparts for those who want to go deeper.
This is sort of a false dichotomy when you compare the two or say that they can't be compatible. In fact, they have to be compatible. Traditional Christians are, in fact, Gnostic. They claim to know for a fact that god exists, and that it exactly what a Gnostic is.
The church will of course argue that it provides services which men cannot provide for themselves. That is the justification. However, when looking from an outside perspective, what does the church do? It interprets the bible and reminds people how to successfully get into heaven. I've got a few friends that interpret things and a smartphone for reminders. Worshippers can do just fine without a place to worship. A place to worship, however, cannot survive without worshippers. That is the fear of the church and why they are incompatible.