I've been told recently by my kid's speech therapist that if kids don't pickup how to properly pronounce harder-to-say sounds like L and R up to 14 yo, they'll

I've been told recently by my kid's speech therapist that if kids don't pickup how to properly pronounce harder-to-say sounds like L and R up to 14 yo, they'll probably never learn it. Which leads to the same conclusion, because I guess learning an accent is basically learning how to modify the way you make speech sounds.