Also, no one is mentioning that there is still a significant amount of "translating" that has to happen. My kids all picked up language pretty quickly, but unless you are familiar enough with their specific pronunciation and vocabulary, it still sounds like baby talk to outsiders.

For example, last night when I got my 2yo out of the bath, he asked me for help putting on his favorite pajamas, if he could have a cookie, and asked to watch his favorite music video before bed, all in one sentence. But if you didn't know he pronounces pajamas as "comfy cozies," cookies are called "treat from under the stairs" and "hear wheelie rainbow neckshun" means watching Willie Nelson's cover of "Rainbow Connection," then of course it would sound like gibberish.

A baby's babbling can express fairly sophisticated grammar and sentence structure if you meet them halfway. And frankly, making it clear that you can understand them expressing their ideas in their own words is highly valuable when it comes to raising healthy, confident kids.