I wish it wasn't so but I do think to the degree you can declare something dead the lean startup is. The problem is that lean startups requires a number of things that aren't accessible anymore.

A) Maybe the most important is time. You need time in a good environment to actually develop something. Which has become a lot more costly.

B) Large companies are controlling more areas than ever. People often wary of regulation as a barrier, but as time goes by the market participants creates their own barriers. Many areas are just harder to have an impact in than it used to be.

C) And then there is just competition, especially for things like talent.

I guess it isn't the lean startup that is dead so much as the environment for it. You can say the same thing about co-operatives, non-profits, community establishments and a lot of other things that are good ideas (probably more so than ever) but not able to flourish because of other interests.