The trends Rebol was trying to push back against, for its time...might seem passe now because some of it is (publicly) absorbed by those it influenced. It was a retaliation against things like XML that was flawed from the start or C++ name mangling. Or basically any other trend of that era where Carl perceived (rightly or wrongly, or half-right-wrongly) as people doing some "leap before you look" introductions of junk.
It had a reactionary bent to it. And that reactionary bent inspired Douglas Crockford (a Reboler back in the day) to make JSON.
Some of the more practical aspects that might have interested many people about it then, has likely been absorbed and improved upon other places. But it's good to know what it was before understanding where Ren-C is taking it.