I mean, it was written by a Christian and the first book was published 1950.
The 1949 law was passed in the UK barring marriage under 16, and went into effect 1/1/50.
Knowing Lewis the entire reason for the "Susan problem" was him likely being upset child marriage had been (slightly more) outlawed.
So Susan turned 16 and Lewis made a big deal about a sudden change and now she's an adult.
Granted, I could very well be wrong.
But it seems like somebody upset about progress, and I wouldn't be the first to label Lewis as such. But it's hard for anyone to claim he wasn't using his writing to shoehorn his opinions in and get kids to agree with him.