Clojure projects can start with literally no files (not even a deps.edn). By default, you get Clojure as a dep and src/ as a directory. Run `clj` to get a repl. If you make a function, you can call it with `clj -X my.ns/foo`. If you push it to github, others can consume it immediately by using your git url + sha.

There are lots of other things - they are all additive. Many Clojure libraries and tools don't need a build.clj or tools.build at all.

My experience is that deps.edn is much easier to get started with. With a template from something like clj-new you can get testing, a basic jar building script, etc to get started with and it's all there for you to muck with if needed.