I'm by no means an expert on this, but I was under the impression that Wittgenstein meant that language was an insufficient tool to express the "things we must pass over in silence", e.g. metaphysics, religion, ethics etc., but that he nevertheless believed that these were the only things worth talking about. My understanding was that he believed that language is only good for dealing with the world of hard facts and the natural sciences and, while we cannot use it to express certain things, some of these things might be "shown" by different means, in line with his comment that the unwritten part of the tractatus was the most important part.

This conclusion from one of hist lectures largely sums up how I would understand his view of many of the "things we must pass over in silence".

"This running against the walls of our cage is perfectly, absolutely hopeless. Ethics so far as it springs from the desire to say something about the ultimate meaning of life, the absolute good, the absolute valuable, can be no science. What it says does not add to our knowledge in any sense. But it is a document of a tendency in the human mind which I personally cannot help respecting deeply and I would not for my life ridicule it."

This is largely the way I have been led to interpret it through reading other people's interpretations and it is probably wrong, but I thought that I'd try and express it here, because I do have a strong desire to expand my knowledge of Wittgensteinian philosophy. One thing which I do think is quite likely though, is that Wittgenstein would consider any written "interpretation" of his work to ultimately be "nonsense" insofar as any written part of it is concerned.