If documents like the Constitution didn't need interpretation, lawyers wouldn't exist, and neither would there be any point for the Supreme Court because meanings would be so obvious so as to never require any debate whatsoever.

Sorry, but your rant shows a simplicity of thinking in the context of complexity. It would be great if language was akin to mathematics, but it just isn't. Language is non-Aristotelian, meaning A does not always equal A.

Example: Apple = Apple. That seems to be pretty obvious right? But apples can be quite different from each other. They can be different sizes, shapes, and colors. They can also vary according to a temporal dimension. An apple right now is not going to be the same apple in a year.

Definitions also drift with time. A word right now is not going to necessarily mean the same thing 100 years from now. Definitions are not set in stone.

So yeah, the words we use require actual thinking.