Hmmm, this is a very fraught topic and could easily derail this thread. My "Catholic Grimoire" thread might be the place for it.
That is where I put Jake, whom I happen to like.
When reading Jake - at least his early writing - what I took away was an additive rather than subtractive mythic interpretive layer, that came from his use of the techniques of comparative religion. He maybe went too far emphasizing the Greek threads of the grimoires, but it is in there.
The GV is an Italian, Southern European grimoire, and he felt it "preserved more of the older Greek Goetia." He probably overstated the case for this, but I will say the Greek concepts of Hell/Hades are very close to the Catholic concept of Hell/Purgatory, and all probably came from the same Orphic / Hellenic / Neoplatonic substrate that gave us both. One does not have to "go pagan" to get there, but by reading the pre-Christian writers and concepts, as the Church Fathers certainly did, can help sound out a cosmo-conception.
Personal Gnosis Warning:
If you ask the daimons of the GV what they are, they'll sometimes say they're beings left over from the Primordial Darkness who build reality - and I'm sometimes inclined to think they are not joking. In my view, what they "really are" are manifestations and lower emanations of the ancient primordial Time God, the Demiurge, who precedes these later names and comes to us through the Church from a prior Earth age. He is the original Creator God that created all later creator gods and the daimons.
So, in my view, Jake is just using different names for the same Creator God. He is far more pagan than I, but his "solve" for the Catholicism of the GV was to add a Thelemic Greco-Egyptian Neoplatonic framework. If that seems strange I would just point out St. Paul, who pretty much gave us Catholicism, was a Hellenized magician whose letters are soaked in Neoplatonic concepts like the
Pleroma,
Aeons, and
ascent through the heavens. I do not want to say it IS literally the same thing all the way through, but it kind of is.
So, I just don't see the problem unless one has a hardline fundamentalist theological view, either pagan or Christian.
Jake's Thelemic Greco-Hellenic system works, but they also run around a bit more, I have found. Probably because his "high philosophical pagan" structure is missing the Catholicism's far more Demirugic and rather violent expression, which I also adore. Mary is the nice part.

All that that was just part of the ambient culture the GV came from, but I have no issue with people finding other cultural expressions of the same powers that simply exist "in the universe" . Pagans are nice people and usually have real personal theological issues clustering around the legitimate use of violence and other Saturn / Mars Demiurgic expressions.