The reason that I would personally argue that atheism is not a worldview is it is directed at a very specific part of life (belief in God/Gods).
For me, a worldview should be a general approach, e.g. the best way to evaluate the truth of something is rationally based on available evidence or the most moral way to treat people is to be kind/gentle/caring, etc, etc.
Another example of a worldview which is one I do not subscribe to is Gordon Gekko’s “Greed is good” from Wall Street.
