>Few people value having such a solid ANSI standard when it doesn't include modern stuff like iterators/extensible sequences, regexps or threads/atomics.
For everyone: are there plans to include such topics in the Standard, or are there canonical extensions that people are using?
CL-PPCRE for regular expressions.
Bordeaux-threads for threads.
Alexandria for various miscellaneous stuff.
Trivia for pattern matching.
CFFI for, well, FFI.
And Series for functional iterative sequence-like data structures.
There's also ASDF and UIOP, but I'm not sure whether or not they're part of the Standard.
I would also add iterate to the "must haves". All noobs should constantly look at the CLHS (available for dash, zeal and emacs too!), https://lispcookbook.github.io/cl-cookbook/ and https://github.com/CodyReichert/awesome-cl, anyway.
Truly, someone could tie himself to SBCL and its extensions and get a much more modern environment, but I think it's worth targeting ECL and CCL in addition.