Does "at its most rococo" mean "at its most fanciful (form)"?

Youre pretty much right,rococo has a few meanings , and in your quote's context I believe it refers more to the term meaning , like,"Uselessly ornamented", or "garishly busy with useless detail ". Rococo architecture, in the early 1700's was a French celebration of many types of styles and materials in design and ornamentation. The architecture used masonry next to stucco and had gilded and ormolu decorations so as to overwhelm the eye.(But, in most cases, nothing was "bearing")

Its since gone from being a purely descriptive term to being a pejorative term.

I agree with farmerman. Uselessly elaborate with little or no functional substance. Theologians debating about how whether or not angels have gender, etc. The elaborate appearance could be used to distract people from its uselessness.

Thank you both.