It seems that if one is going to depend on science and mathematics, my understanding is the position held by most people who work on the big issues in the realm of the testable is that it's likely that there are hard limits as to what is to be known. Often referred to are Godel's Theorem or Turning Halting States where some mathematical problems are unsolvable. Or I've heard of computations so hard to make that if we could turn every atom in the universe into a computational machine we still couldn't know such answers. If this is all true, the testable and measurable are not completely knowable and thus I Don't Know is the default position as none can be truly gnostic.
And since there is no way to measure or test claims which are unmeasurable or untestable, it is impossible to determine whether they are true or not. This would mean that those claims are also unknowable. Making on some level agnosticism an unavoidable consequence all around to everyone.
On the other hand, part of why I'd consider myself an atheist is the dark horse in the race that could possibly win. That is the position that we don't know that all things are not actually knowable particularly if there are ways to measure which are unmeasurable by current standards. Or that we may be able to finally dismiss other things that we now suppose cannot be measured against some future certainty. Consider that the scientific method is only 400 years old. Arguably it and the math that supports it were not widely used until the industrial revolution was revved up an running. We've had game changers come along such as General Relativity and Quantum physics. And since then human knowledge in that realm and technology have been increasing exponentially and have changed the world vastly beyond all other human endeavors since our ancestors came down from the trees and walked upright. Science has an excellent track record. So who's to say what might be known given merely another 400 years? Or 4000 years or 50,000 or a million years from now? Or even 20 years for that matter.
We might be able to cross off the notions of a creator as the
Ultraviolet Catastrophe was crossed off the list of expected phenomenon once Max Plank helped overturn classical physics with modern physics. Perhaps, at least in certain instances, could Godel or Turning be overturned? (I know, not at all credible at this point, but who here is absolutely gnostic about what we'll learn eventually?) Or perhaps we'll even find a subtle but universal footprint of a creator of the universe.
In any case, I say it's way too early for anyone to be making assumptions of what is knowable or unknowable, at least until science and math have run their course as much as that is possible. Call it agnosticism-plus. If it turns out that our descendants can know 98% about everything that is someday, that should be a comfortable amount of evidence to make pretty good assumptions about the rest. And who can say that it won't be 100%? Despite the high confidence that this is currently impossible (and that is my personal default position) on the other hand, you never know.