Then you are changing the nature of unicorns.

Sure, as is my right. This is what happens with religion constantly. For example, Pope Benedict XVI believes in evolution and the big bang. These remove the domain of God from creating all creatures, the earth, etc. Sure, it still leaves room for God to start it all off, but it is changing a fundamental aspect of creation. It's the god of the gaps.

There are 20 major religions

There are currently 20 major religions. There have been many more through human history. The vast majority don't exist anymore. Two of those, Islam and Christianity (plus Judaism), believe in the same god. Abrahamic religion all comes from previous religions though. You can compare the stories in the Bible to stories of other beliefs in the region and they match, though some aspect vary. Religion evolves. (Which I'd argue is evidence that it isn't correct. If it were correct it'd never change.)

The prevalent existence of spirituality in Ethnic Tribes is an argument for spiritual element in humans. I will assume that we are in agreement on that point.

I agree it's an argument for humans to believe in something spiritual, but not that it's accurate. We don't need to explain lightning with something in the sky fighting or anything anymore. We don't need to explain mountains with gods having risen from them or anything anymore. Spirituality in humans is evidence of humans wanting an explanation for things, regardless of their knowledge of how it actually came to be, and nothing more.

It also gave me personally some benefit to my mental well being.

That's good. For me it was only a negative influence. It didn't make me feel better and only told me what to do. I don't agree with many morals the Bible teaches (and neither do most Christians), and I'd rather have morals that treat people well regardless of what they or I believe. I don't need religion to constrain my behavior, and it would prevent me from doing things I want to do and cause me to do things I don't want to do.

If it's a positive for you then fine, though I'd argue there's probably some other religions that have better effects. When I was poking at religious beliefs when I was a teenager I really liked Buddhism. It's a much more relaxing religion and makes much fewer claims and demands. That's how I became an atheist though is I learned about other religions and noticed they all have equally valid claims, so I just don't believe any.