What's up with the anti-lisp trolling the last few days? Looks like someone is really bored...
For the record: Nobody says Lisp will allow you to do something that cannot be done with C, just that usually you'll do things with Lisp, you rather wouldn't want to with C.
And regarding the "open ended nature" of Lisp, my guess is that the combination of regular and reader macros allow lisp to adapt far better without needing the standard to change. As a C user, you are on the one hand limited by what the standard decided to give you (try implementing a macro on the level of loop in te C preprocessor), but at the same time you have to struggle with what the standard decided to unspecify, calling into question how reliable your software will be in the long run.