Well no, every time you have a chain of functions in your call stack that all do

    if(f(blah) != E_OK) {
      return E_WHATEVER;
    }

(which is veeeery common in C) you are reimplementing exceptions by hand (and with less performance in the no-error case since you still pay for the branches, while a C++ code with exceptions would just be a sequence of function calls without branches in that case)

I wouldn't disagree with you. The OP said that programming languages w/o exceptions aren't successful. C doesn't use exceptions, it has it's own way of dealing with similar issues, and yet it's quite successful.