I'm not the first to note, but...

One should instead proceed as follows: I exist, and among my properties are that I experience what I am experiencing, and that there is a sequence of such experiences. If I can free my mind from the assumption that the known classes of abstract object are all that can possibly exist, what sort of entity do I appear to be?

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Thus a person could say, for example, that the passage of time is an illusion (that's denial)

I fail to see where you think the denialism lies, but I'd guess you have misunderstood what it means that passage of time is an illusion. It doesn't mean we can't experience passage of time. It doesn't mean we're not the kinda entities that experience passage of time. It just means that the stuff we intuitively deduce from our experience there is rubbish. The same way people tend to think that sight is something that goes from the eyes to the object you're looking at. Erroneous deduction from very real experience.

Maybe elaborating on your views might help? It seems that inferential distance is kinda big, at least too big for me to handle