I think that some, though definitely not all, of the pagan community’s general uneasiness regarding UPG (unverified personal gnosis) is because of the ambiguity and uncertainty that comes with it. Interpretation of lore can vary greatly due to the issues of translation, competing scholarly theories, and similar matters, but it is often much easier to place our trust in sources that have been debated and defended for centuries than it is to accept the diverse and sometimes contradictory personal epiphanies of other current, living pagans.
This is not necessarily a bad thing. Unease with this ambiguity is what leads many pagans to research their gnosis, to find out if it coincides with what has already been known in lore, and so would be VPG (verified personal gnosis). The same unease is also what leads many pagans whose experiences cannot be verified in lore to look into the UPG of others, where they may find that their own experience is mirrored in those of others—PCPG (peer-corroborated personal gnosis) or SPG (shared personal gnosis).
My personal theory, though by no means authoritative, is that the most prevalent PCPG/SPG of the distant past is what was seen as important enough to be written down, and as a consequence, became the lore of many traditions. Similarly, conflicting PCPG/SPG may well have helped contribute to schisms and the creation of sects.
There can be a tendency to see this as a shattering of something whole, a wonderful truth cut apart that needs to be reassembled and mended. This is where I fear that the desire for certainty can lead us astray.
The pursuit of comprehensive, universal belief and practice—catholic, in the lowercase dictionary sense—can too easily lead into fundamentalism and a resistance to change. After all, once the One And Only Truth is discovered, it must remain true forever. It cannot be that it was true once, but is no longer, or that it is true now, but will cease to be in the future. It cannot grow, and must never adapt.
Such a rigid and static system is tempting to fall into precisely because what it offers is comforting. It is safe. One never has to worry that a belief may be wrong. One never has to re-examine their experience, their practice, their reasons for doing things as they do. There are no personal conflicts when there can be no disagreement, and potentially painful examination of oneself and one’s needs, wants, and overall motives becomes utterly unnecessary. The One Single True Way will take care of us for us, like a stern guardian, even though it will also mean giving up personal freedoms.
I admit that, although such practice will by its nature deny the very possibility, this may be beneficial for some people in certain times of their lives. The comforting restrictiveness may be able to act like a cast around a broken leg, holding it in place until bone knits and flesh heals. But eventually the cast must come off, and one must begin to walk despite the difficulty, and work through the uneasiness and stumbling. Otherwise, the muscles will atrophy, and instead of healing, we will sicken and die inside.