Tools/devices - metaphors: the author would compare the tiger to many things it wasn't even closely related to. -jargon: you could tell the poem was from a long time ago and not form 2000-2015 - symbolism: the author would mention a black smith but that black smith would represent the creator of the tiger.
Opinion I do agree with the author a little. I do wonder why the tiger is so interesting. But I don't wonder who created it, I would be more interested in how the universe came to be.