As a sef-described Catholic, why aren't you in line with the Vatican's stance on evolution?
Catholics don't have to accept the theory of evolution if they don't want to. It's neither a matter of faith nor morals, so whatever the Church says about its vailidity is not binding of the conscience.
However, given that at least three popes have asserted that evolution IS compatible with the faith, Catholics have to "religiously submit their mind and will" to this proposition. It would not be a sin, however, for a Catholic to reject the theory while at the same time aknowledging that it would not in conflict with Catholicism if true.