I don't disagree with this, but connecting an MCU Magneto to the Holocaust would require an extra layer of nonsense beyond the "Where have you been" to figure out how a 90 year old is so spry and ready to go. Even though my idea isn't much better, looking back at it. Denzel is too young to be a magneto birthed froma childhood lost in Sudan or Rwanda. Apartheid isn't in the same ball park and he isn't Cambodian, but that time frame would work. Maybe Asian Magneto can show up in Shang-Chi and the Ten Rings.
I'd still prefer Ian McKellan's old ass show up through some portal tho. Or maybe Magneto is from Nazi earth. Dr. Strange is gonna introduce a multiverse for real, right?