Can we once and for all retire the "I want my teen Sims to look 12 years old" thing?

Depends entirely on what you want teens to look like, 13/14 year olds look very different to 17 year olds so if you want younger teens you'll probably want them to be shorter whereas if you want them to be 16/17 you'll probably want them to be taller.

For me personally I prefer my teens to look more like 14 year olds as otherwise theres not much distinction between them and young adults so I have height sliders to make them look younger but that's just my preference