The “drastic cooling” does not yet exist so while the theory may be strong it is still just a theory.
That's the thing, though. It's not a theory. The earth goes through a repeating pattern of cyclical climate variations that are written into the geologic record.
Real climate scientists have studied that record for decades, and can point you to exactly where we are on that recurring cycle right now.
Those studies are bolstered by observations and measurements of the sun's activity, which also goes through a recurring pattern of behaviors. Those behaviors are the primary driver of climate patterns on our planet, and correlate perfectly with them.
Climatologists are not formulating predictions of an impending solar minimum based on computer models. No, they're reading the actual record. What comes next is written right there in front of them. There is no guesswork, and the conclusions are inescapable -- we're entering a new era of extreme cold.