Agnosticism sounds eminently reasonable, especially to anyone who’s attracted to political centrism or who’s used to compromising and avoiding conflict. But it’s demonstrably false, if only because the central, most absurd theistic definitions of God are incoherent, so denying that such self-contradictory gods exist is eminently reasonable.
But I agree that evidence for or against God is often ambiguous. As you say, proof of God might always be better construed as proof of aliens or “angels” or a demiurge.
The thing is, the whole scientistic enterprise of “proving” God’s existence with arguments and evidence is wrongheaded. Theism is supposed to rest on faith, not knowledge. We’re supposed to round out our rational worldviews with aesthetically-pleasing stories (fictions), since rational methods don’t provide complete answers to all questions.
When the reasons run out, we can be agnostic like Data from Star Trek or we can take an irrational leap of faith and admit we’re emotionally compelled by some fiction or other. The question, then, is which fiction is worthy and which is obsolete or otherwise flawed or tainted. Which myth speaks to our zeitgeist? That was Nietzsche’s question.