For starters, Mormonism denies that there is a transcendent creator God who is the maker of all things visible and invisible, as said in the Creed. Instead Mormonism posits an infinite succession of finite gods who were all originally men. Indeed, Mormonism rejects the idea of anything being created at all but instead posits that “the elements are eternal” (D&C 93:33), in other words, the now-discredited theory of the
steady state universe.
There is no satisfactory explanation for the Big Bang in Mormonism. Nor is there a good Mormon explanation for democracy, as there is no Creator in Mormonism from who come inalienable rights, just a series of men who became better than you.
Thus, both the Big Bang and the nature of democracy as stated in the Declaration of Independence are compelling arguments against Mormonism.
For that matter, it would be accurate to say that Mormonism is actually atheistic, because its definition of divinity does not posit a transcendent creator God.
But with that said, remember that many Mormons are actually “cafeteria LDS” and are somewhere between Mormonism and Christianity just as many self-proclaimed Catholics are somewhere between Catholicism and Protestantism. For that reason, they may or may not agree with Mormon cosmology, but as far as the official LDS doctrine goes, that’s how it is.