I have no problem with Conservation of that-which-exists. But since animated Mass-Energy is eventually embalmed as cold dead Entropy, I can't accept it as eternally existing, in any constructive sense. That single "substance" of reality may be conserved as it flips back & forth between Cause & Effect --- subsequent to the original Instantiation. But when & where did it do its phase changing prior to the point-of-beginning of space-time?
Presumably, in the mathematical Singularity there was no actual mass or energy, only statistical Potential. Once their flip-flopping has begun, there is one-more-thing necessary : the Laws that regulate when & how they change. Unregulated change would result in random chaos. So, "responsible believers" agree that Mass-Energy exists only in space-time, which is destined to end in Heat Death (max Entropy). Who or what was the Lawmaker or Potentiator?
↪180 Proof responds to my criticism of the fringes of cutting-edge science as-if I reject the work of serious scientists for religious reasons. But, I have no religion. So, my criticism is merely Philosophical. And is focused on implicit assumptions rather than pragmatic utility. For example, I am dubious of feeble attempts to explain away the Creation Event, by postulating an infinite regression of Big Bangs (question begging??). Since they have no empirical evidence of anything beyond the bounds of our known universe, my layman's guess is as good as their expert shot-in-the-dark.
My typical response to the Complexity-from-Simplicity question is to define the Ultimate Singularity. Just as you are a singular Self composed of millions of interacting parts, the Whole of which our world is an active part is a Singularity : no parts, just Potential (Tendency not Actuality). So, I think space-time Mass-Energy is dependent on infinite-eternal Potential. Nothing comes from Nothing; but Everything comes from Potential.
Singularity : where the curvature of spacetime becomes infinite.
Coincidence vs Creation :
Physicists tend to take Matter & Energy for granted, without questioning their origins, or their philosophical meaning. Matter is merely the furniture of Nature. Energy is the builder of natural things. But as Materialists, they have a problem with the Laws of Nature, since laws are normally found only in human Culture. Laws are aspects of human thought & behavior, as exemplified in Government and Religion.