Step 1: recognize that all life needs to consume energy from somewhere (regardless of Carbon based or AI ones)
Step 2: realize that albeit the total energy contained in the universe is probably going to be enough for any civilization out there, regardless of type, the total amount of energy that the CURRENT TECH LEVEL allows to harvester is never going to be really large enough to treat it as infinity.
Step 3: assume that some individuals of any civilization wants to grab as much energy for itself as possible.
Step 4: Combine 2 and 3, and we reach the conclusion that the said individuals will always try to bar others from gaining enough energy, which means an expansion of the gap between the "rich" and "poor", and most importantly lead to a shrink of education of the "poor"s can benefit from, and ultimately destroy the "tech base" of any civilization. The "tech base" is the least amount of individuals that can generate some tech/science genius like Einstein/Newton who can propel the civilization forward greatly.
Step 5: I'd argue that this destruction of "tech base" almost surely occurs before the civilization reaches the point that general AI (or whatever that can substitute the original "tech base") arrives.
Step 6: Tech/Science advances slowly afterwards and ultimately the civilization won't reach very far into the depth of the universe.