In some cases yes and some no
The main idea of a poem is for the author to get a point across to the reader. The poem is supposed to give emotion or a feeling towards the reader. The author wants the reader to understand what point he or she is trying to make. People can learn important lessons or phrases from poems. It gives the reader a more deeper understanding of what they are reading. In summary, the main idea is what the author is trying to teach or personify towards you.
Deprecating means disapproving.
Rumor has it that Lady Bracknell was a combination of Wilde's own mother, Lady Wilde, and Lord Alfred's own mother, Lady Queensberry. Seems like his mother takes the cake on the dead-on character for this