There are many schools of Daoism and there is a distinction as well within the history of Daoism among Philosophical Daoism, Religious Daoism, and Alchemical Daoism. At bottom Daoism is a naturalistic philosophy. There is no sense in Philosophical Daoism of any kind of diety of any stripe. The Dao is sort of an abstract unifying name for whatever life and consciousness are and perhaps the "principles" one observes in the universe. There are some schools of Daoism which are "mystical" and I would agree they are just another religion.
The concern of Daoism is more with discerning the "patterns" of the way things work and living in concert with those patterns as part of the natural order rather than separate from it as in Christianity. Most Daoism really doesn't deal with Cosmology or origins except what might be learned from a study of nature, in other words, science. Daoism is not irrational nor is it contrary to science. There is a recognition that there may be things you can learn by observation of your own consciousness in meditation.
So, yes, there are probably some who turn to Daoism because they want to be religious but can't stand the other major religions. However, as I understand it, Daoism proper is not a religion in any sense. Actually neither is Buddhism in it's original form. Daoism is not dogmatic. It is based on observation and experience which is open to be tested by anyone.
I'm an atheist with tao. I never found a reason to study Taoism as the tao te ching works for me. I accept the existence of things beyond my understanding, which is nothing other than a proper foundation. tao is a utility of conceptual engineering. Start from the unity of self to build essential dualities in concept to bring self more into alignment with tao. tao is the essence of motion, it's the rhythm of the universe; it's the one to the many to the one to the many... the heartbeat of the self organizing system. It is evolution, it is emergence; it is the would-be-flap of wing of butterfly you catch in your hand before the turbulence builds to typhoon. tao is a word beyond saying, a sound beyond hearing, a place beyond being; the thing of no-thing that carries your mind from void...
tao is balance, harmony, beauty; a space between, previously unseen.
Or is that too eastern? How does pure mathematics sound, better? There ain't nothing about tao that ain't real, but some people don't like math, either. ;)
I think there is a tendency within the atheist community to dismiss certain things off hand because they have religious baggage. Daoism is one of those things. The Four Noble Truths are another. There is no need to "throw the baby out with the bath water". I find Daoism to be an incredibly rewarding personal philosophy just as I find the Four Noble Truths to be an absolutely accurate understanding of the human condition. Even the various deities that have attached themselves to Daoism and Buddhism are helpful as metaphor. Think of Athena. I don't think anyone still thinks she really exists but few other characters can express the ideals she represents as poetically. Life will never, ever be four white walls and a neon light-bulb. Life and people are colorful. Some things will always be better understood poetically and *cough* spiritually rather than mutually agreed upon black and white definitions.
It would be easy to dismiss something as being "too Eastern", but I think that betrays a certain arrogance in Western thinking. For too long we've had this idea that we were 100% right about everything. From the "missionaries" who told indigenous peoples to "kiss the cross or kiss the sword" to putting native lands to "proper use", it has always been a matter of civilizing and modernizing the rest of the world to adopt OUR values without taking the time to at least examine the worth of those that are being replaced.
As a minority, we atheists are forced to defend what we are not, but we cannot fully define ourselves by it. In other words, "Atheist" only says what I am not. "Daoist" and to a large degree "Buddhist" says what I am. In some ways I am even a "Red Letter Christian". The practical application of these ideals is that I am able to do my tiny part in making the world just a little bit better. This is something that I feel atheism, all by itself, is insufficient in doing.
Sorry for the novel :)