Note that this says nothing about their usefulness for developing software.
You said that they didn't share code, libraries, books, or community. First off, they do share community to some degree: there's a good bit of overlap between all of them. It's not all overlap, but there's plenty there.
Second off, you know what other languages don't share code, library, or books with the Common Lisp we know today? MACLisp. Interlisp. Portable Standard Lisp. Lisp 1.5. Emacs Lisp. AutoLisp. ISLISP. Eulisp. Arc. To say nothing of Hy, LFE, MDL, Newlisp, NIL, Picolisp, and yes, Clojure and Scheme. And there are countless others.
Lisp has always been a language of many different dialects. Why should we pretend it's any different now?
Same for English dialects.
For Germanic languages this is not the case. English and German are both Germanic, but knowing German does not let me read English literature.
Lisp is like English: a basic vocabulary, a basic syntax, basic semantics understood by all readers. I can look at some basic Lisp code and I will understand the program. A Lisp developer looking at Clojure code will understand very very little.
Maclisp shared code with Common Lisp. For a lot of stuff there was a single code base at MIT for several Lisp dialects, including Maclisp. After some time Maclisp development ended and sharing ended. For example the source code for the complex LOOP macro was at one time a single file for Maclisp, NIL, Lisp Machine Lisp and Common Lisp.
People ported programs from Maclisp to CL by changing them or by translating them with tools, not by rewriting them.
There were also code bases which worked both in early Scheme and CL.
Emacs Lisp has a huge CL subset and even includes a version of CLOS. Since both Emacs Lisp and Common Lisp are coming from Maclisp, both languages are very similar anyway. Basic operators are the same, differing in various details - like dialects often do.
Common Lisp had Interlisp compatibility packages, while Interlisp was still used. There were translators, too.
Xerox had Interlisp and Common Lisp integrated in one Lisp.
Kent Pitman wrote an ISLISP compatibility package for Common Lisp.
There are compatibility packages for Portable Standard Lisp, which allow the unchanged use of PSL code in Common Lisp.
etc etc
There is zero code sharing between Lisp, Clojure and Racket. Compatibility with the Lisp 1, Lisp 1.5, Maclisp, Common Lisp, Emacs Lisp, CL, ISLISP, main line of Lisp wasn't a goal for Clojure and Racket. That's fine. They got rid of historical baggage and could design new languages.
Basic rule: if a language has LISP in its name, there is some chance that it actually is a LISP.
People usually name their language LISP something, to give the impression that the language is compatible with Lisp. They use different names, when the language is different: Scheme, Javascript, Logo, Dylan, Clojure, ...
Take a Lisp 1.5 manual, look at the function index and check which functions and special forms are provided. If most of those are absent (or doing something different), it's not a Lisp: append, atom, car, cdr, cond, cons, eq, eval, intern, list, load, map, member, pair, print, read, prog, quote, reverse, return, set, setq, trace, ...
Clojure fails at (iii), as it just propagates Java exceptions, but I don't think that is impossible to fix, so not a fundamental flaw. JVM is too heavy, and that is a problem for some. Otherwise, it's a well thought-out Lisp with a thriving community and some cool guys and a BDFL (i.e. Hickey).
Common Lisp excels at all the three of the items I listed, plus it's batteries included and has lots of libraries around. Also, it has a standard, so that you can develop on SBCL and deploy with Clozure CL or CMU CL. It's downside is there's some historical baggage and there are no DHH or Hickey or Torvalds in the community, which isn't a downside for me, even an upside.
To say that there's compatability between Scheme and CL, and no compatability with Racket is ridiculus: Racket has Scheme compatability modes.
As for the language being called Lisp if it's Lisp, two of the examples you list in the "non lisp" category do so: Clojure's website claims it is a "dialect of lisp," and AIM-349 describes scheme as "essentially a full-funarg LISP."
As make no mistake, all of these languages, from Common Lisp to Clojure to Scheme, are dialects. They have the same origins, and they share many of the same ideas.
