I don't understand modern religion

Do people who follow religions, whether it be someone who worships once every month or several times, actually believe in God or a genuine higher being?

I grew up a Christian, which sect exactly, I'm not sure. I remember growing up and having doubts if God is real, then being told it's a sin to doubt in his existence. That led me on a path to atheism. Now, to me, it doesn't make sense how billions of people believe in a person that is all powerful and all seeing, but they have no definitive proof of. It's all based on stories or myths. To me, it's just like Greek and Roman Gods, which we know do not exist. To me, its a very similar situation with God as the Tooth Fairy or Santa Claus.

Do people believe that God is real? Or do they worship the idea of God?

I'm not trying to tear down people's beliefs and I'm not trying to question in an offensive way. I do not have an agenda, I'm just a little confused and curious as someone who 100% does not believe in a higher power. I want to understand the beliefs of others.