Babies and those who can't speak, can't express themselves adequately. Imagine being an adult who cannot speak, because of paralysis or (in past centuries) having your tongue cut out. Imagine being wheel chair bound and no speaking machine like Professor Hawkins had.
Imagine not being able to speak to your wife or husband, how you feel, how you appreciate every little thing they do.
Words enable thought; words are the vehicles by which we express thoughts. The more words we know, the more accurately and precisely can we feel our feelings and express our personalities.
Some things cannot be expressed in words alone. Some feelings are expressed only in body language, and I remember a phrase (1 Corinthians 2:10) which goes "who among men knows the thoughts of a man except the spirit of the man...". Some things can't be expressed in words, like pain, groans, joy, etc. but they are felt.
Sometimes I can't think how I feel in English. I can only express it in Spanish words or Russian words, because it is a different feeling in English, it is not the same feeling or thought in English.
You are right, to really think one needs language. Language is what sorts out emotions. Every person who cared for a baby does that spontaneously. A baby is crying, the mother/father goes and says to him « what is going on? You just wake up darling, let’s see what is bothering you, do you want me to take you in my arms? Maybe you are a little bit hungry » . The baby doesn’t know how he feels, he needs words that give sense to his emotions and his feelings .That’s reassuring. Gradually he will understand what the adults says, hunger, tiredness will have a name with the prmise that the caregiver will try to solve these problems.