I'm an A-level English Literature student who studied power and conflict poetry 2 years ago.
"Tissue" draws a comparison between the fragility of paper and the fragility of human life. It talks about the importance of paper as a literal idea, while constantly reminding the reader over how fragile it is. The ideas grow bigger into descriptions of buildings and religious imagery, with the poet ending with talking about human skin, perhaps suggesting how human life and the impacts it has are far stronger and longer lasting than built structures. There are really several interpretations, and I suggest looking at BBC bite size and other revision resources to explore the different themes and quotes that link to these.
I think it would be a good poem to compare to "Ozymandias" as both poems explore the impacts of human lives and how they can (or cannot) transcend time and nature. Have a look at both poems and see if you can find any links.
I don't blame you for finding it complicated: I barely understood it when I was yr 11 and even now it seems to fit more with my A-level poetry anthology than the GCSE one
I hope this helps!