I thought the “beetle in the box” argument was pretty much aimed at 5 year olds:
I have a beetle in my matchbox, but I can’t show it to you.
You have a beetle in your box too. You can’t show me yours either.
How, then, do we compare beetles? How do we even know that we (all) have beetles?
because as we talk about ‘our’ beetles, it becomes clear that we are talking about the same thing. Language is not a thing we do on our own; we do it together. What a word ‘means’ is determined by how we use the word.
If we both decide to call the things in our boxes ‘beetles’, since the word fits, we both might as well have beetles.