"Even C++ offers nearly everything that LISP does at this point; other than live code tree modification through macros, which aren’t anywhere near as powerful as C++’s algorithm and container library IMO, LISP has even lost the expression gap to C++ at this point."
As someone who has professionally been a C++ programmer and a lisp programmer, all I can do is laugh. The reason people like lisp is the basically infinitely mutable syntax we can build to fit specific target domains. It's still a radically different approach that most languages don't really touch. The only places I really see the "let's hack as a sub-language not as a framework" approach routinely is in the Ruby and Io communities.
Every C++ templating approach is a trivial macro hack. And macros get nearly all the benefits of C++ templates (including static analysis).
As for why lisp has been left behind in favor of other languages? Well, it's pretty much the same reason as why few people in America wear bowler hats these days, they're out of fashion. That's it. It's history, it's fashion, there isn't any good technical reason why! Most current lisp implementations are very competitive with their peers in most arenas. There are some social issues (the lisp communities are very fragmented, which makes it difficult for beginners to get traction).
It is true that stripped-down languages with almost no runtime features (e.g., C, C++ when you ignore dynamic_cast, etc) can produce "faster" code than lisp (meaning "does less with more lines of code, but executes quickly on modern hardware"), and that's good for them. But it's not like some kind of special privledge, _everyone_ uses C to bind into their language and make it fast. It's the native underpinnings of most modern operating systems, so this shouldn't be shocking.
Quoting again: "LISP is dead. If you really need a LISP, move to a modern LISP such as Clojure or Scala, or a modern near-lisp like Ruby. You’ll learn a lot about what LISP had kept from you."
I get the strong impression that this author doesn't like lisp (he probably knows it to some degree, but not well enough to really grok it). He freely and interchangeably mentions Scala, Ruby and Clojure as "replacements" to lisp. Clojure aside, mentioning Scala and Ruby in this way is ludicrous, and betrays a sore lack of insight into what lisp is and what the current state of lisp technology is. Anyone who looks at PLT Scheme and SBCL and doesn't see a fairly modern and powerful system (in PLT Scheme's case with some practical and interesting work on contract-based programming), then they're deliberately not looking.