Running `just` will invoke the first recipe, so you need to add one that invokes `just --list` for this to work — see https://just.systems/man/en/listing-available-recipes.html and my sibling comment.
Just what?
"Oh... come on! Just... <waving hands angrily>"
Pretty clear to me :).
But even so it would have been a better design for `make` to list top level targets or something.