On balance, both theories were ill-advised attempts to portray short-term minor changes as large-scale major pattern shifts. The real drivers of large-scale change are much slower in their impact and if we get really lucky, our presence on the planet will overcome the next glacial episode which we can expect in about ten to thirty thousand years from now.
I think anyone will agree that this is the least of our worries on this particular planet at this point in history.
“Science” has sailed blithely along in its assumptions that the output of the sun itself hasn’t been fluctuating.
But why should we hypothesize that? The ability to measure anything objectively hasn’t been around long enough to compare how the sun shined on a scale of 10,000 year increments. Whatever is roiling around in the heart of the sun as it consumes its fuel could not be verifiably modeled. If the sun was dimming for previous ice ages and dims again, there ain’t going to be anything we can physically do about it. Modern technology, and nothing less, would suffice to keep humanity alive.