I do agree that initial impressions are important for a language and "perceived" learning curve does make a difference. Things that scare people away initially do hurt adoption; things like Clojure's syntax and that it is a dynamic language on the JVM (i.e. how does that affect interop/performance/etc) all raise questions. Even if there are answers to these questions and justified reasons just like most sales pitches you've already lost a lot of people who have doubts and are already productive as they are.

As an example I remember a presentation done some time ago where the presenter was showing code in F# and many non-technical people understood the code thinking it was a pseudo code at first (i.e. business stakeholders/BA types/etc). That was a win for them. If I showed F# and Clojure code side by side to an ex-coder manager as an example syntax I'm sure would matter and they often have a say in this decision. Buy-in is an important criteria in language selection for sure, as well as current skilled developers. If the pool of devs is small how easy it is to train people and get people wanting to be trained in it thinking it may be dead end skill with no jobs? I don't have that opinion personally but some dev's definitely do. Especially because jobs in these languages are scarce; if learning curve is small then it could be used even then.

My cynicism shows marketing and perception of a tech stack are equally if not more important than other factors in tech selection in many companies. No one got fired for picking IBM or in this day and age Java?