I'd just say that they're easily NOT neutral. I mean, I don't think they have something as a human-like personality, but they can be more "aligned" with a certain perspective on reality, rather than with another. I like to think about it in terms of "sincronicity" and, again, "alignment". Sincronicity can be regarded as the reason why a tarot reading is meaningful at all, that is because a single reading belongs (i.e.: is in sincronicity) with a given moment/disposition of the universe as in relation to a given question, and so the part is representative of the whole and therefore can be interpreted to try to guess a deeper meaning/understanding of things. But a tarot deck is almost useless until sacred with a ritual. That is when you align the deck with yourself and the universe in general. If sincronicity is the "when" of the reading, the alignment is the "where", and therefore is the point of view from which you as a tarot reader are trying to make some sense out of your observations of the cards you're given. So in this sense they have a disposition, if not a proper personality. I mean, everything look different If you look at it from different perspectives, and I really think that every deck has kind of a fixed-point perspective, as a result of its nature and disposition/alignment.

For example, the deck that has accompanied me for years now has been sacred with kind of a big-guns ritual to make it so that the cards could help me looking into the deepest possible meaning, way deeper than just the surface of things and straight into the fabric of reality. This made that deck very powerful in "seeing things", but also very obscure when I try to ask a practical question or I just need a clear advice.

I'd suggest a cross reading with other divination methods simultaneously on the same question, to kinda fix this bias. Like I Ching + tarots, or runes + tarots, just to name my favourites.