In my view, we need to find the answer to your point from Quran, and Muslim recorded traditions.
The Quran claims to be guidance for all humanity.
As regards to claiming it to be 'timeless', nothing in the Quran as far as I know exist that claims the Shria Law is everlastingly beneficial. There are verses in Quran, that alludes the Rites are beneficial to an appointed time, which according to recorded Hadithes, the appointed time, is when the Mahdi comes, with a new Book and new teachings.
The Quran claims to be a clear Book, but at the same time it says some of its verses are figurative, and no one knows their interpretations except those who God has given them knowledge and calls them 'Well-grounded in knowledge". In another word, Quran is a clear Book to understand. So, for instance, it clearly says, some of its verses are figurative, and to know their interpretation, you need to learn from the well-grounded in knowledge. Is this not clear enough to understand? But, what happened in Islam, everyone uses his own mind to interpret rather than learning from the Well grounded in knowledge who according to Traditions, and even the Quran, are the progeny of Muhammad.