Agnostics also have to assume that a human brain is capable of weighing evidence in a reasonable way.
If you adopt a perspective of totalising scepticism then, of course, you will shrink into a solipsistic disbelief of everything. But the fact there is no Archimedean foundation of knowledge doesn't mean we ought to treat all truth claims equal. There are logical and mathematical truths that are a condition of the world being intelligible to us, and that structure the internal working of nature insofar as we can understand it. We can have justified beliefs about many things, but we cannot have a justified belief in God, which requires dogmatic faith.
Also, there are glaring internal contradictions in the major world religions. If God is good and omnipotent, then why is there pain and suffering? How can God be one and three things at the same time, as the doctrine of the Trinity tells us?
Be careful if you truly want to find the answers to those questions, it is a dangerous road.
Think of Jesus as just a literary character in an epic myth. I could care less if you don’t believe in the things as facts. Most christians I know believe in a factual Jesus without believing in the mythical Jesus.
What actually makes this mythical character from classical literature so appealing? Don’t read the book as a bunch of facts, think about what it means. It is less relevant to me that the creation of Adam was a literal creation from dust, and not some step in the evolution of biological life, it is what that mythical character means, what he represents to our psyche that is of first importance.
This really isn't the place for this discussion, but I can see evidence that at least suggests something that looks like logic or rational thought exists. The ability of people to seem to be able to do simple arithmetic is evidence for both. I don't need faith in it, I'm aware the world could exist with both things being an illusion.
The existence of God is something that it's nearly impossible to even imagine what external evidence for it would truly be. It relies solely on internal faith.
That said, I don't like the wholesale write off of faith as "delusions to make you happy." Just because I can't understand it doesn't necessarily make it rubbish.
If you’re homeless, and treated like crap left and right, by yourself and others, lacking in the dignity every human deserves, the idea that a god (a king) would care about the lowest of low, and even be on your side is something powerful.
The ability to not crumble under suffering from oppressive evil men, and instead have it be your glory, is not easy with no idea of a good god. That is why the story of blacks in America is glorious. They endured through hell, again and again (even after slavery), and now have the potential to be a powerful people if they can cast off that which binds them. The pessimist says they’re victims, the optimists says they are and can be victors.