I agree with you (and I've been researching Earley parsing and Pratt top-down operator precedence parsers lately), but: one thing at a time. While learning, it may be more helpful to experiment with AST transformations in Lisp and get immediate results, and wait on parsing until they get to the syntax design.
Also, too many toy interpreters/compilers mess around with syntax but have really conventional semantics. I suspect if people don't sink so much time into parsing etc. first, they may be more likely to focus on semantics instead.
I'm not so sure about that.
People chance the sytax because that's an unfront difference between their language and others. Changing the semantics requires a leap for what can be perceive as little benefit (e.g. people will say "isn't this just C++ but with garbage collection?").
Eh. As far as I'm concerned, if the only difference is the syntax, what's the point? But I'm comfortable with the Erlang, K, Lisp, C, and Forth syntax, so "I grafted Ruby syntax on X" is pretty underwhelming.
Also, too many toy interpreters/compilers mess around with syntax but have really conventional semantics. I suspect if people don't sink so much time into parsing etc. first, they may be more likely to focus on semantics instead.