You're looking at aggregate. There are specific types of goods, the lack thereof, that's driving up the CPI. Right now I hear the car prices in US are pretty high and the production is lower because of the chip shortage.
The supply for a lot of other things is pretty elastic.
[1] https://www.semiconductors.org/chipmakers-are-ramping-up-pro...
> Why isn't this excess demand (caused by too much free money) as opposed to a "shortage"?
It might very well be excess demand. The idea is that supply should always be elastic and grow to meet the demand. In this case it didn't.
But this "excess demand" can't be attributable to lower interest rates because people, I imagine, aren't borrowing to buy these goods.