Either the universe is eternal, God is eternal, or something came from nothing.
I get you CA . . .
But the nature of "eternal" doen't necessarily mean something is ever-present. The components of the physical world may be part of an eternal cycle. The best way to picture eternity is as a ring rather than a straight line (which has a beginning and end and therfore not eternal). Any point on that cycle or ring, may bear absolutely no resemblance to another . . . but is connected, or gives rise to, the next phase in the cycle.
In practical terms of the universe . . . we already see through cosmology (with it's unique view through time as well as space) that the universe has been through such phases . . . where the molecular elements that make up the universe we see today have not yet even come into existence. What came before the big bang? . . . maybe a contracting universe . . . and round and round the cycle of eternity continues. We can only see a very small section of that cycle from our current vantage point.
That eternity is subject to such cycles is not such a radical concept . . . we see these cycles in all parts of the physical world already.
I feel this concept needs to be taken seriously . . . that eternity does not mean that something is ever-present or constant. In order to attribute meaningful purpose to life . . . we often feel the need for the ever-present constant of a God concept . . . something unchanging and in control.