It's modern morality, I'm afraid. Yes, nowadays we think 16 year old having sexual contact with people 10+ years older is terrible, but when I was young in the late 60s/70s no one thought twice about it.
This was a hit in 1973/1974 when the Ringo was 33/34. I never heard a word of controversy about it either then or since:
"Okay, well, this is for you
And it's also for the other girls who are young as hot
And it's called 'You're Sixteen', you're beautiful and you're mine
Whoo!
You come on like a dream
Peaches and cream
Lips like strawberry wine
You're sixteen, you're beautiful, and you're mine (ooh, mine, all mine)
You're all ribbons and curls (ooh)
Ooh, what a girl (ooh)
Eyes that sparkle and shine (ooh)
You're sixteen, so beautiful and you're mine (ooh)
Mine all mine, mine, mine, mine
You're my baby, you're my pet (ooh, wah, wah)
We fell in love on the night we met (ooh, wah, wah, wah)
You touched my hand, my heart went pop (ooh)
Ooh, when we kissed, I could not stop (ooh)
You walked out of my dreams, and into my arms (ahh)
Now you're my angel divine (ahh)
You're sixteen, you're beautiful, and you're mine (ooh wah, wah, wah)
You're my baby, you're my pet (ooh wah, wah, wah)
We fell in love on the night we met (ooh, we fell in love)
You touched my hand, my heart went pop (ooh, what a night, ooh, what a night)
Ooh, when we kissed I could not stop (ooh-ooh)
You walked out of my dreams, and into my car (ahh)
Now you're my angel divine
You're sixteen, so beautiful, and you're mine (ooh wah, wah, wah)
You're sixteen, so beautiful, and you're mine (ooh wah, wah, wah)
You're sixteen, so beautiful, and you're mine (ooh wah, wah, wah)
Thank you"
Source: Musixmatch
Songwriters: Richard M. Sherman / Robert B. Sherman
You're Sixteen lyrics © Warner-tamerlane Publishing Corp., Mijac Music