> a lot of people think about JVM with verbose slow VM code that works in the enterprise

They are severely misinformed, then, and it would be a good deed to give them an opportunity to learn more about this.

Which is: Java is fast. Its startup time is impressive, and the runtime performance is generally also good. RAM usage could be less impressive, but I read that it can be optimized for memory consumption, achieving pretty good results - I don't have any experience here, so I can't really say.

Anyway, my problem with Java, is that it is not designed to be used on its own. To use it, you need a build system, and the language doesn't give you one; which is why there are many different systems, which you need to navigate somehow. Having to learn these build system (XML? custom Groovy implementation?) is what made me dislike Java. It's not that different in C++ or C#, but it adds to the feeling that you work with an ancient technology, not a modern one.

That's however not the problem with Clojure - it at least has a single build system + package manager - Leiningen. To me, what disqualifies it, is the startup time of its REPL. Well, that's only because I have a luxury of not needing to do anything on the JVM - so I'm speaking from a position of a hobbyist polyglot programmer considering new languages to learn. I would probably reconsider if I had a job where JVM would be a must, but the specific language was not yet chosen (how probable that would be is another matter). Anyway, back on topic: I don't have Clojure on this machine, but last time I tried it, it took more than a second before the prompt appeared. That is slow even when considered on its own, but it borders ludicrous (speed) when compared with other Lisps, which seems to be the right frame of reference here. In that comparison, it's... Well, just to let you know how bad it is, Common Lisp and Chicken Scheme, two Lisps I do have on this machine, have startup (+ shutdown!) times like this:

-▶ time sbcl --eval "(exit)"
This is SBCL 1.4.6-1.fc28, an implementation of ANSI Common Lisp.
More information about SBCL is available at <http://www.sbcl.org/>.

SBCL is free software, provided as is, with absolutely no warranty.
It is mostly in the public domain; some portions are provided under
BSD-style licenses. See the CREDITS and COPYING files in the
distribution for more information.
sbcl --eval "(exit)" 0,00s user 0,00s system 94% cpu 0,006 total

-▶ time csi -e "(exit)"
csi -e "(exit)" 0,00s user 0,00s system 93% cpu 0,005 total

Now, two things:

1) I get it that "you're supposed to have a deamon process in the background, so you don't need to start that often", but this, in itself, is basically announcing surrender. In Common Lisp you're supposed to do the same, but not by necessity!

2) Yes, I tried alternative runtimes/implementations. Indeed, they are better. However, until they get, provably, 99% the same semantics as the reference implementation, they won't be adopted by any significant amount of people, which has enough of the drawbacks to make me not seriously consider using them. Anecdotally, last time I looked, I've seen lots of lein plugins for setting up projects with ClojureScript on the frontend and some (pure) Clojure Web framework on the backend. There has to be a reason behind that.

TLDR: Java is very fast, Clojure uses JVM in ways which are inherently slow on that VM, but refuses to honestly migrate to a more suitable platform, because of Java ecosystem, which is also a major selling point of the language.

At least, that's my understanding of the situation - if I'm wrong, I'd be happy to get corrected.