Skepticism is a general approach to the world, and not exclusively linked to ‘denial of God’. Most of the people are skeptics except in a few walks of life. As what Richard Dawkins said concerning atheism, all monotheistic religious people are skeptical of all other religion, and all other gods except that of their own. Thus, Muslims are skeptical of Krishna, Hindus are skeptical of Muhammad, and Jews are skeptical of Jesus. Skeptics are skeptical of all of them. In other words, all religious people are skeptics minus one!
Without skepticism, people cannot survive. All most all successful people are skeptics in all aspects of life except one. They are N-1 skeptic, where ‘N’ all evidence-free beliefs in the world. Skeptics, on the contrary, are skeptical of the N-0, where none of the beliefs are left out. I.e., they are skeptical of all ‘belief’ systems. This include ‘beliefs’ in ‘scientific socialism’ or in the ability of ‘revolutionaries’ to build a just society when they come to power. In other words, God-denying communists cannot be called ‘skeptics,’ because they maintain a belief which is unfounded by reasonable evidence.
Skepticism is the general approach of science, the most successful enterprise of mankind. Science does not believe in phenomena without adequate and replicable evidence. Peer review systems of scientific journals advocate applying an approach a general disbelief in claims unless it is founded on unassailable evidence. The unassailable evidence is usually overwhelming and replicable.
Skepticism agrees that there is the vast vista of the universe that cannot be fully understood at any moment in time. But they do not consider this as a reason to believe in something without substantial grounds. Of these areas of ignorance, they keep an open outlook, tending to keep many things ‘unknown’ rather than ‘filling’ their ignorance with ‘knowledge-like’ beliefs.