Atheist attacks against theism and religion are too simplistic because they fail to address sophisticated theological ideas. Atheists only attack superficial religious beliefs because they are easy targets. By ignoring sophisticated theology, they don't really undermine true religion.
Whenever atheists criticize or attack religion, religious beliefs, or theism, religious theists of course seek some way to respond. Sometimes they may able to show that the atheists' arguments are unsound in some manner, but very often they have to acknowledge the validity of criticisms of particular religious beliefs and doctrines. At this point, it becomes common to argue that atheists are attacking only simplistic versions of religion, not the "real" and sophisticated versions.
This sort of response allows believers to imagine that somewhere out there is a sophisticated, complex, and wonderful set of religious beliefs which is just too much for atheists to handle. There are two significant problems with this, however. First is the fact that all of this alleged sophistication generally has little to do with religion and theism as they are actually practiced "in the trenches" in the pews and lives of actual religious believers.
Even if atheists are attacking "weaker" forms of religious beliefs and arguments, they are not attacking Straw Men because they are dealing with things which people actually believe. If there is a problem here, then, it's not with atheists who are simply addressing religion as it is actually practiced, but with religious believers who are practicing such "unsophisticated" versions of religion. Instead of chastising atheists, why aren't they chastising believers? Why aren't they bringing these sophisticated beliefs to others?
I see religious believers attacking atheists like Richard Dawkins for not addressing sophisticated theological arguments and ideas, but I don't see these same believers writing letters attacking religious theists who promote the sorts of beliefs and ideas which Dawkins criticizes. If detailed knowledge of sophisticated theology is necessary before criticizing religion and theism, why isn't is necessary before adopting a religion and professing some sort of theism? We can turn this around and ask why theists can criticize atheism without being able to demonstrate a knowledge of more sophisticated atheistic philosophy and arguments against gods?
Atheists are being held to a very different and much higher standard than theists. Apparently it's okay to believe and promote religious theism without experience with sophisticated theology, and it's okay to criticize atheism without being familiar with sophisticated atheistic philosophy, but it's not okay to be critical of religious theism unless one understands sophisticated theology. This suggests that the real problem with atheists is not their criticism of "unsophisticated" religion, but rather how they undermine popular religious beliefs.
The second significant problem is how these "sophisticated" religious beliefs, ideas, and arguments may ultimately all be quite beside the point. The most sophisticated version of a bad idea doesn't rescue that idea from being bad; the most sophisticated belief in something false doesn't rescue that belief from being false. Even if we grant that there are indeed genuinely sophisticated theological ideas, arguments, and beliefs, none of that matters if the ideas and arguments are bad and beliefs are false.
What religious believers in particular, those who argue that atheists must address their more sophisticated theologies must do is link their ideas, beliefs, and arguments to something that actually exists in the real world. The fact that some theological concept is highly developed and sophisticated doesn't mean that it's about anything outside human imagination. To be more specific, religious believers cannot rebut atheist critiques of religious theism by saying that they have very sophisticated and complex conceptions of God which atheists haven't addressed. Atheists don't need to address those conceptions of God unless and until believers are able to demonstrate that there is something out there which we need a sophisticated conception of.
PZ Myers calls this the "Courtier's Reply," describing a possible response from a courtier to a boy's observation that the Emperor is not wearing any clothes: "He has apparently not read the detailed discourses of Count Roderigo of Seville on the exquisite and exotic leathers of the Emperor's boots, nor does he give a moment's consideration to Bellini's masterwork, On the Luminescence of the Emperor's Feathered Hat. We have entire schools dedicated to writing learned treatises on the beauty of the Emperor's raiment, and every major newspaper runs a section dedicated to imperial fashion..."
We can grant that all these treatises are indeed sophisticated and well-developed, but unless there is actual clothing to describe, they are nothing but highly detailed discussions about imaginary fabrics, not sophisticated discussions about anything that exists. You don't need to read, understand, and address sophisticated works on textiles to observe that the Emperor is naked. You don't need to read, understand, and address sophisticated works on astrology to observe that there is nothing to it and that the stars do not even influence, much less direct, our lives.
You also don't need to read, understand, and address sophisticated theological works to note that there's no evidence of any gods, that religious theism hasn't provided any such evidence over the years, and that everything we know is more consistent with the absence rather than the presence of any gods in the universe. Bringing up "sophisticated" theology is just an attempt to move discussion away from claims about the existence of gods and towards claims about the nature of gods. Unfortunately, claims about the nature of gods don't matter if there are no gods and unless the existence of something that needs to be explained as a god can be pointed to.