I think you are right, in general and in normal circumstances. But I've read the the pandemic had an impact upon very young children and their immune systems. By being quarantined and masked for a few years of their early lives, they did not create the immune responses that most infants and toddlers get while they grow.
So it's being said that 3, 4, 5 and 6 yr olds are being hit hard by the flu and other contagious strains that they'd normally be able to easily ward off.
Here is one article as an example:
The CDC warned Wednesday that RSV cases are increasing in infants and young children in Florida and Georgia, possibly a sign of the start of the RSV season nationally.
abcnews.go.com
The CDC said it wants clinicians and caregivers to be aware of RSV because it can be particularly dangerous for babies, young children and older adults.
Last year, RSV also appeared earlier than usual, spiking in October before declining in November. At the time, experts told ABC News that this might have occurred because children were not exposed to potential infection between 2020 and 2022 due to lockdowns, or because they were born during the pandemic.