First of all, no shit. I don't think anyone has really debated that it was a factor, or even a major factor. However, this doesn't end the debate on how much other factors played in to it including supervolcanism in modern day India (the Deccan traps) or the already dwindling numbers of dinosaurs species that led up to the Chicxulub impact. So this leaves the debate right where it was before, with the Chicxulub impact being a player but also other players without a defined role.
I don't know if she's a one-off, but wikipedia cites Gerta Keller as arguing that the Chicxulub impact may have had little to do with the extinction event, as it looks like there's another 300,000 years of material deposited in between the iridiuum layer marking the impact and the end-Cretaceous. To quote her from
this article on the Geological Society's webpage:
Conventional wisdom holds that any such large impact leaving a 175km-diameter crater would cause major mass extinctions. But this hypothesis is based solely upon the assumption that Chicxulub was the K-T killer. None of the other major mass extinctions in Earth history is associated with major impacts. This hypothesis has no empirical support and must be considered false — at least with respect to Chicxulub.
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