I can only share my experiences, but build tools and running a repl are fairly low on the confusion list for those new to coding with Clojure. At ClojureBridge London we have introduced over 300 students who are either new to coding or on their first language. We had been using Leiningen for a long time and now use Clojure CLI and Leiningen, Clojure CLI is far quicker to install and run, deps.edn has less in it so is easier to explain. As there are numerous plugins (aliases), it's much easier to gradually introduce new features into how Clojure is used. We only really use clj-new and figwheel-main You can also have both Leiningen and deps.edn configuration in a project, so there is a very simple migration (especially if there are relatively few dependencies). If you have invested a lot of time learning Leiningen or rely heavily on Leiningen plugins that do some magic, like lein-ring, then switching to deps.edn configuration does require a bit of effort, but you don't have to switch.