And yet here you are on a site designed to invite religious views and opinions.
I agree that atheism is not a religion, but it can be and sometimes is practiced similarly. And often in terms of it's dogmatic 'evangelism'.
Most atheist do, but that is not a logically supportable position. And no matter how many times I point out why it's not logical, they ignore me and continue right on believing it. Because in spite of all their claims of "unbelief", they are in fact "true believers" of their atheism.
If God exists, God's nature and existence is a mystery to us. So we invent ideas and images and characterizations in our minds to represent and 'stand in' for that mystery. And often, people forget that their imaginary representations are imaginary representations. It's just human nature, I guess.
There is no logical reason to presume these imaginary representations should be similar, or agree. Why would they be? And there is no logical reason to confuse them with the actual possibility of God, though people often do.
And the same goes for religion. Religions are just collections of ideas and images and rituals and practices that people can use to help them live life according to their chosen theology (God concept). And again, there is no reason to expect these religions to agree with each other.
They are all different people's solution to the question of the existence and nature of God. And no one knows if any of them are accurate, including the atheist's solution. So they all remain possible. No one gets to be right. All that really matters is what God-question response is the right one for each of us?
Theism is not about what anyone believes. Theism is a philosophical proposition. It is the proposition that God/gods exist, and in a way that matters to us. If we accept the validity of that proposition, we call ourselves theists. If we reject that proposition as invalid, we call ourselves atheists. If we neither accept nor reject it because we lack sufficient information to determine the validity of the proposition, we call ourselves agnostic.
Belief really has nothing to do with it. Belief is just a proclamation of our own presumed righteousness. When we say "I believe" all we're really saying is that "I am now convinced that I am right".
And that's not really relevant to the question of God's existence or nature, or much of anything else.
The problem is that people don't bother to recognize the difference between a proposed ideal, and a personal belief system based on the ideal. And because it all becomes personal to them, their egos get involved. And the ego's job is to maintain a sense of righteousness no matter what. So then any discussion become a pointless, endless, battle to be right.
We use words to communicate. The more precisely we use them, the better able we will be to understand each other's ideas. But the ego-boxers aren't trying to understand anything. They just want to be right. Making linguistic communication difficult. As they change the meaning of the terms to better support their own views.
I explain and clarify the terms using logic but they don't care. They just want to "win the argument" and if that means bending and changing the definitions and logic of the terms, that's what they'll do.