There is a nice irony also, that JA surely intended, for our amusement, by her linkage of Gilpin with Collins, showing us what her discerning eye revealed to her about Gilpin's floridly pompous prose, i.e., it is anything BUT picturesque!

I will also add that it is also a fine Gilpin-invoking bookend to the following line spoken by Lizzy 8 chapters earlier, at the very end of Chapter 10 of P&P, which was noted on the RoP allusions page:

"The picturesque would be spoilt by admitting a fourth"

The context is that Lizzy has playfully invoked Gilpin in refusing to pick up on Darcy’s polite attempt to counteract Miss Hurst's rude abandonment of Lizzy, and to include Lizzy in a stroll outside with him and the Bingley sisters.