There was true innovation, both technically and aesthetically, not just retro-ing and appropriation of other hipster movements (9 months after they stopped being cool)
What hath tumblr wrought? Rap used to be the vanguard; now it's fallen into the same trap as rock and house music, emulating history and trend-chasing. Sure, there have always been trend-chasing rappers, but the trends they used to chase were new trends within hip-hop, not from the indie world or hip-hop's history books. When early '00s indie rap became obsessed with the early '90s, it was cool that the torch was being carried, even if it was underground; when everyone is doing the same two decades later, it's become a cultural reblog.
And it isn't just the surface-level retro aesthetics that have taken over; a rapper's delivery and performance style, once the entire basis of their relevance, have taken a backseat to their ability to go viral, to generate headlines and to appeal to a class of bloggers and media folks. There are, of course, exceptions—Danny Brown is one rapper who has a distinct identity, for example—but distinctive personalities, versatile rap styles and novel deliveries no longer seem as vital. Style is no longer substance; taste has taken over.