There are many that would strongly object to this conclusion. I have heard friends describe their inner life as almost entirely verbal, that they "think in words", and are totally unable to relate to anything else.
When we say "communication", I think there is an implication that the goal is communication with others. But there is also value in communication with oneself. To verbalize is to condense ones thoughts into words, and when we hear words they get unpacked and evoke meaning. The resulting feedback loop can be amazing for refining ideas.
It should be no surprise that humans might end up relying on this internal monologue when thinking to the point that they mistake it for thought itself.