After Willoughby leaves Barton Cottage on their first visit and Elinor is jokingly commenting on how well he and Marianne got along, she remarks "you have received every assurance of his admiring Pope no more than is proper."

The poet Alexander Pope was well-known and, although he had died in 1744, had been very popular. However, during the Romantic period he fell out of fashion for various reasons. His writing was considered too formal and Marianne's favourite Cowper thought his style of writing was too high-brow and that the language of poetry should be more accessible to the common people.

The Romantics preferred poetry to have more imagination and more passionate language than Pope's style.

I think it's interesting that in S&S2, one of the couples Marianne mentions in her speech about how love is to burn and to be on fire like Romeo and Juliet, etc. one of the couples she mentions are Eloise and Abelard, who were made famous in a poem written by Pope. I've linked an online version of it here. To me, this seems like something that would appeal to Marianne:

Eloisa to Abelard

However, another poem by Pope was "The Rape of the Lock" which is basically about a Baron who takes a pair of scissors and snips a long lock of a young lady (Belinda)'s hair as a kind of a trophy. Because he does this without her permission, she becomes very upset, and a battle ensues.