Having had Delta with the the original vaccine, I don't agree with the last part at all.
Here are my theories:
1) Lockdowns, especially locking down low at-risk kids, kept the virus in the field a lot longer and gave it a lot more time to mutate than if it were to have run the natural cycle of a flu strain.
2) The original vaccine didn't have nearly the efficacy against Delta as original Covid, and virologists were slow to react and come up with a Delta vaccine.
3) Flooding the country with infected invaders at the start of 2021 was criminal homicidal negligence. The kind of negligence we should have burned Cuomo for.