There have been a lot of "modern" libraries within Common Lisp, but there isn't a coherent way to "look at" them together.
So the impression of CL as this "frozen in time" language persists (I think of it more as a system than a language, but still).
CIEL is one attempt, by Vindarel (who's also making a video course at Udemy and contributes a lot to the Cookbook), to bring together "the best bits" from libraries such as alexandria, serapeum, cl-json, access, uiop, trivial-do, ppcre, bordeaux-threads, lparallel, fiveam, and more.
See the documentation for details on all these features. If all you've known is the old, bare-bones CL, you're in for a surprise.
This, or something like it, is sorely needed, to have a "pseudo-standard" to allow people to write "similar-looking code", without having CLHS as the only common ground. I wish him luck.
P.S. I made some quality-of-life improvements in a personal fork, based on my attempt to get this working on my MacBook.