Dylan Byers wrote an article entitled Vox not living up to the hype, explained. The title pretty much sums up the content. It's been getting a lot of mostly negative attention from journalists who cover the state of the media, a number of whom have pointed out that a five month old news site which has been steadily growing in popularity (and which passed Politico this month in unique visitors) would be hard to call a failure.
I think the article is about more than Vox.com, though. I've written a more extensive critique of the article here, but to sum it up, Byers writes a few paragraph in which unnamed journalists and editors are asserted to have stated that nothing was new about Vox. The tone of that part of the article could be summed up as "Get off my lawn!!!!".
My read on the article is that it's really about the anxiety the traditional print media is feeling about the rise of the web-only news media. Revenues are plunging in all traditional media, but newpapers and news magazines are being hit particularly hard. There is an undercurrent of resentment that the best known writers in print media are moving toward web-only publications, and the Byers article seems to reflect that resentment.
The issue of whether the "cards" on Vox are a novel approach is a red herring. I don't think any of the writers there have ever claimed that explanatory journalism was a new and unique invention.
But the Byers article has the phantom industry insiders constructing that straw man.