It is difficult to imagine any well-informed person making this charge. Through his pontificate, one of John Paul II’s overriding concerns has been the proper implementation of the Second Vatican Council.
The person that you have encountered is either being disingenuous, has a distorted understanding of what things were like before Vatican II, has a distorted view of what Vatican II and subsequent legislation did, has a distorted view of what John Paul II has been doing, or some combination thereof.
To mount a defense of the Holy Father’s actions in this regard, one might pose the following question: If John Paul II is "trying to go back to the days before Vatican II," what are some specific examples on this? What legitimately developed doctrines or disciples has he returned to the state they had before the Council?
If a person wants to make a generalized charge like the one under discussion, he will need to produce a large number of examples. A few examples of minor importance will not establish that the pontiff is attempting to undo the work of an ecumenical council. Of course, since the charge is preposterous on its face, the person will be unable to produce the kind of examples needed.
If he names a large number of examples, there will be something wrong with the great majority of them. For example, he may be spuriously reporting something that the Holy Father is rumored to want (rumors about what the pontiff does or doesn’t want or like are notoriously unreliable and should be avoided by parties on all sides). He may have in mind that the Holy Father did something that he did not in fact do. He may perceive an action of the pontiff as "reversing" a post-Vatican II "trend" that was never authorized to begin with and which—likely—was contrary to the wishes of the Council itself. Or he may have an erroneous notion of what the period before the Council was like and may perceive things as a "return" to that state which in fact are not.
Most likely the person you have encountered is simply fantasizing about what a post-Conciliar church should be like and then throwing brickbats at the Holy Father for adhering to the vision Vatican II in fact mapped out for the Church.