Tarahumara - "why such a talented and influential musician is not more famous"
The book I just read has several passages say on this subject.
..... Rameau, like Bach a master of the “late baroque”, came at the end of a period; at his death the gates of fashion closed remorselessly upon him and, like Bach, if he survived at all, it was only in trifles. Luckier than he, Bach has risen again and seen as complete a revival as a dead musician can ever know....
.... A public very remote from Louis XIV's wanted an art more superficially and more sensuously attractive. To use the current jargon, "Rokokomenschen" were tired of "barock" art. Their criticism of it has a documentary interest of the sort which attaches to post-1918 criticisms of Wagner and Beethoven by a generation weary of hearing their music and of listening to their praises....
Then started the era of Mozart & Beethoven, of course. (See timeline). Especially Mozart's music proved most enduring, imho, because of its relatively far simpler, catchy tunes, almost entirely on the major scale.
Philosopher Jean-Jacques Rousseau who fancied himself a bit of a composer criticised Rameau's music as having "trop de notes" (too many notes) 
Then again, that was not an unbiased view: Rousseau and Rameau conflicted on some work (Rameau got commissioned for them when Rousseau thought he would be) and Rousseau remained a bitter enemy of Rameau until the very end.
Rameau's music was criticised as "that of a geometer, as mathematical music, as what would be called today une musique cérébrale ", and the "mediocrity" of Italian music was celebrated.
As the book says:
.... In the nineteenth century the name was still remembered at least as much as theorist as composer, but it was only a name; the music was forgotten and the books unread. In the night that overcame French music as a result of the Bouffonists’ triumph, the great era of the sixteenth, seventeenth and early eighteenth centuries was as if it had never been.....
(Bouffonists = Supporters of Italian opera buffa)