For the sake of the less experienced, I'd point them to these substitutions in particular:
Compojure: Reitit (which they used in the front end too, so migration maybe in progress) would be my preference for backend routing.
Component: Integrant takes Component's ideas, but prefers the flexibility of multimethods operating on plain data to the typed records approach for defining systems.
Schema: Once very popular, but superseded by clojure.spec (bigger in scope) and to a lesser degree Malli for data schemas.
Potemkin: Avoid, handy for some internal code organisation purposes but hostile to tooling and debugging IMO.