Lisp in general is not the epitome of simplicity. Lisp-2s like Common Lisp add some cognitive load for those used to simpler languages (although Lisp-2s have their advantages).
And of course, Lisps that include meta-object protocols (Flavours, Common Lisp again, &c.) deliver power, very elegantly, but for people unfamiliar with them, there is a learning curve to climb.
You're mistaking Lisp for a programming language. Which Lisp is not. Lisp is an idea (or rather a set of ideas), based on which different PLs can be implemented.
I'm perfectly aware of that. My point stands - using a concrete language to generalize over some abstract ideas might be confusing for those who are unfamiliar. In general, Lisp dialects strive for simplicity.
That is exactly the reason why Scheme was chosen for SICP.
Elegance is not always synonymous with simplicity. For example, Smalltalk’s use of Class and Metaclass is very elegant, but most programmers encountering this for the first time would not call it “simple.”
After they got over the hump and grok how the two things work together to serve as the foundation for Smalltalk’s OOP and allow programmers to alter Smalltalk’s OOP... Then the elegance emerges.
I think elegance is a measure of the simplicity of a tool relative to the complexity of the problem domain, whereas simplicity feels like a more absolute measure.
And of course, Lisps that include meta-object protocols (Flavours, Common Lisp again, &c.) deliver power, very elegantly, but for people unfamiliar with them, there is a learning curve to climb.