For me (and lots of other people, too) Clojure is a fantastically acceptable flavor of LISP.
"... It’s an astoundingly high-quality language, sure—in fact, I’m beginning to think it’s the best I’ve ever seen..."
Not sure what he thinks now.
Now our cup runneth over. Common Lisp is the same as it was while Clojure and Racket offer ways to a lispy future.
What makes these languages different is their vibrant communities. I do hope they get faster implementations out sometime :) (and allow people the freedom they've been used to in the CL world).
I still do think that we need some new Lisps to do new stuff which can then be cherry picked and so on by new Lisps though.
But the great thing about Lisps is that they can't get stuck in the past.
For example, if, say, Python didn't have decorators and you wanted to add them in, you'd have to present the idea in a PEP, get approval from Guido, write some code, et cetera. In Common Lisp, you just write some reader macros and that's it[1]. If Python stopped being maintained, it would lag behind other languages, but the fact that the Common Lisp spec hasn't been updated since 1996 doesn't make it any less modern.
A more relevant example: Lisp doesn't have hash table literals, which every "modern" language these days has, but those can also be added, trivially in less than fifty lines[2] of CL code, and suddenly Common Lisp is modern again.
For things such as hash table literals, you're not supposed to simply have some way of doing it - you're supposed to have a good and commonly used way of how most everyone else would be doing it and representing them in his/her code. Having a bunch of nonobvious, nonstandartized ways alone hurts readability, maintenance and reusability - and thinking that it is okay is a sign of being stuck in the past.
Being able to add it trivially yourself is an order of magnitude worse - because results in everybody rolling out his own. If you want to make an usable ecosystem (not just 'language core') then you have to make sure that for all/most commonly needed things, the default 'batteries included' or 'batteries taken from first google result' work well, not that it's simply possible to get them somehow.