Hi Nature Guy, welcome to the board.
Perhaps it's helpful to make a distinction between what we might call "soft agnostics" and "hard agnostics"?
The soft agnostic might be defined as someone within the theism/atheism system, who isn't sure yet where they belong within that system. The soft agnostic might sometimes be fairly labeled a fence sitter.
I'm inclined to call that person a theist or an atheist, whose faith and/or certainty is weak or wavering. The only way I can see for somebody to drop out of the theism/atheism system entirely is for them to simply say 'I have no opinion about the existence of God'. That seems to me to be pretty unusual. It might work in an abstract sense when it comes to our statements about religious belief, but it's harder for me to imagine how somebody would behave in accordance with it. (If somebody ignores the God-issue, then wouldn't he or she be behaving as if God doesn't exist?)
Some atheists and some theists (sometimes atheists and theists can be very similar to one another) will denounce agnostics as 'fence-sitters' and 'wishy-washy', because the agnostics question the sort of knowledge that (supposedly) justifies the theist's and the atheist's dogmatic certainty. In other words, it's often the gnostic 'true-believer' sort of theists and atheists that don't think very highly of agnostics. But yeah, the more epistemologically modest kind of theists and atheists may indeed see a little agnostic in themselves.
The hard agnostic applies the same test to both theism and atheism, feels that both points of view fail the test, and is thus outside of the theism/atheism system. They aren't fence sitters, because they reject the theist/atheist system that created the fence.
I think that what puts a person inside the theism/atheism system is having a view on whether 'God' (however that word is being used, which often isn't clear) most likely exists or doesn't exist. In other words, theism/atheism is an ontological issue, about the existence or non-existence of something. Gnosticism/agnosticism is is an epistemological issue about knowledge, about whether we possess knowledge of God and about whether God is the sort of thing that's knowable. The thing is, the existence-question and the knowledge-question seem to pretty much be independent variables. So we get (at least) four basic permutations:
It's possible to believe that God exists and that humans have at least some knowledge of God -
gnostic theist. Traditional religious believers who accept divine revelation seem to belong here.
It's possible to believe that God exists, but that God isn't the sort of thing that's knowable by humans (at least in the same conceptual way that we know earthly things, because of God's supposed holiness and transcendence) -
agnostic theist. This one shows up in the traditions of apophatic or 'negative' theology.
It's also possible to believe that God doesn't exist and that humans can have knowledge of God's non-existence -
gnostic atheist. Many of the more dogmatic atheists seem to belong here.
And it's possible to believe that religion's familiar depictions of God most likely don't have any existing referrant, but that more broadly speaking, humans can never really know about the existence or non-existence of supposedly transcendental things -
agnostic atheist. (I'd include myself in this category.)
Some hard agnostics will conclude that nobody knows, and from that conclusion decide to drop what they now perceive to be a pointless discussion. This type of hard agnostic accepts the theist/atheist assumption that the creation of a "knowing" is the point of the inquiry. If no "knowing" is possible, this hard agnostic packs up their gear and goes home.
Other hard agnostics will conclude that nobody knows, accept what they see as a real world fact, and continue the inquiry based upon this information.
I make a distinction between what I call 'strong' and 'weak' agnosticism.
A
weak agnostic thinks that while he or she personally lacks knowledge, it's possible that somebody else does possess it. Or more broadly, even if nobody currently possesses the knowledge, it's possible that somebody might acquire it in the future, if the proper inquiries are undertaken. Regarding religious knowledge, weak agnosticism would seem to characterize the religious seeker.
Strong agnostics believe that not only do they personally lack knowledge, they think that the kind of knowledge in question is probably impossible for human beings to ever possess. I tend to lean towards strong agnosticism, though maybe there's still a little something of the religious seeker in me too.