Or maybe people could just become familiar with ML-style languages? The basic syntax shouldn't take more than an hour or two to pick up.

Well sure, but you could say the same thing about Lisp.

Well they're both the lambda calculus, Lisp just had parentheses.

Does lambda calculus have character strings, structures, exceptions, symbols, mutable variables, quoting code as data, macros and three different kinds of object equality?

it does have symbols

Does it really?

Some of the algorithms for reducing lambda expressions are symbolic, like, say, alpha reduction. But they are not done in lambda calculus itself, as far as I can see; they are done on lambda calculus (by the mathematician, or a machine for manipulating lambda calculus terms).

Analogy: just like ordinary algebra doesn't have symbols; but of course mathematicians work with symbols and so do computer algebra systems.

Since lambda calculus is Turing complete, it can of course represent lambda calculus manipulation (via Goedel numbering of lambda terms and then working with their arithmetic encoding as Church numerals, or whatever).

Ruby has optional parentheses around function parameters (usually it's recommended to avoid parentheses if possible). Shells have no parentheses around command arguments. These languages are mainstream and no one complains about this.

Of course, if we adjust "mainstream" so that it refers to that set of languages which have pass-by-value, strictly evaluated arguments, with no implicit currying, then your point is nearly self-evident. :)

Yes, I agree, that took me also some time to get used to when I dabbled with Haskell and I looked at more complex programs.