I am guessing from => IWantThis
that paramList
is not a val
but an arity-0 method without parentheses:
def paramList: List[IWantThis] = ???
If so, the member is a method type, and you have to get the return type of the method before extracting arguments from it:
val meWantArg = classSymbol.member("paramList": TermName).asMethod.returnType
val TypeRef(_,_,args) = meWantArg