Keep in mind of course that a chart of the risk of serious illness from the flu by age range looks like a saddle. The risk for those 5-49 is pretty low. But the risk for those 0-4 and 50-64 are both much higher.
[1] https://www.nature.com/articles/s41586-020-2918-0/figures/2
I'd still be interested to know if the 0-4 age group has homogeneous risk, or if the real risk is among 0-6 (or 12) month old babies. I have a 2 year old and we have been very cautious, but haven't seen any evidence that kids this age are at much risk for serious illness or death.