Well, I suppose there are two questions going on here.
The original question being 'If we use a tarot deck without reference to it's system, are we really just using it as an oracle deck?'
A further question that arises from the first is 'What is a tarot deck anyway? Is it just defined by the number of cards and suits, or is there more to it than that?'
This second question is interesting as there are many decks that call themselves tarot but deviate in small or great ways from the standard structure.
This second question has been discussed many times before and I believe that the general thought is that the tarot is defined by its suits and it's trumps but that it is flexible enough to allow some changes, some adaptations and still be tarot so long as it adheres to the general structure that we all know and love.
The other question, is using the tarot intuitivley, without regard for the 'official meanings' simply using it as an oracle deck regardless of its true definition.
And there is going to be a lot of disagreement here. There are a lot of intuitive readers, many of whom I have great respect for. And anyway, people are allowed to do whatever the hell they want with their decks.
But all the same, their right to do so does not alter the terms of the question. Are they, in fact, using their tarot decks as tarot, or as oracle decks?
I would say yes, they are using it as an an oracle, the images become springboards for their innate intuition or their psychic faculties or whatever and they disregard the tradition or official or historical meanings of the cards.
If tarot is indeed defined by its structure then to my mind the structure must be there for a reason. The suits, the names, the trumps and the courts must all have some inherent place within this structure and this is provided by the traditional meanings that define the suit of deniers/pentacles/discs to be the suit of the merchants, of money and of the physical realm and so on.
Of course a well designed tarot should reveal these aspects through the art, and therefore should touch the intuitive readers intuition in a way that should trigger thoughts of whatever the card is supposed to be about. However there are some occasions when the intuitive reader will look at a card and be drawn to a single, perhaps insignificant part of the image and their intuition will tell them to take this one aspect out of the context of the card as a whole and because of that they will interpret what would normally be a bad card as a good one. This to me is using the tarot as an oracle.
And it's not to say that this is wrong, it is often damn well right. If you get a gut feeling you ought to go with it. However to read the a card in defiance of its symbolism and its place within the structure of the deck is to step outside the boundaries of tarot and to use it as something other.
Like using a walking stick to thwack a mugger around the head. It might be perfect for the job, it might be exactly the right thing to do in the circumstances but it is not what it was designed for and in the moment of the thwacking it ceases for that time to be a walking stick and becomes a weapon.
But this is just my opinion, and I'm sure other people will disagree.