It seems to me that these examples of illusions and momentary flaws of our perception/processing are somewhat misleading.
The point (my point, at least) is a different one: it´s about
systemic obstacles that don´t allow for a congruence between our ideas and objectivity.
Allow me to attempt an analogy (please keep in mind that 1. it is only an analogy, and 2. it´s not yet an argument - it´s just meant to illustrate what I´m trying to say. Once this is understood, you are welcome to criticize and tackle it, to say "but that´s not the way it is" or "but the analogy is flawed" etc. But first I would like to make sure I am understood.
)
Imagine a device (let´s say a camera, a computer, a printer) both of which are capable only of perceiving and processing in terms of black and white pixels.
This device perceives, develops and expresses its view of a, say oil on canvas painting, in that it photographs, processes and prints a picture of this painting.
(I am/ we are speaking - hypothetically - objectively: we "are" the oil painting as it is, in its three dimensionality, its analogous wealth of colours etc.)
Now, what the heck is "true/objective" about a two dimensional assembly of black and white pixels trying to represent the painting?
It´s missing out on the vast majority of characteristics?
Is that a problem for the device? No. It has captured everything that it can see/process/produce. Possibly, it will be able to "correct illusions" (in that e.g. it decides that a certain black pixel should be replaced by a white one, it may recognize that the camera or the printer do not work as expected etc.), but these will always be corrections that remain within the digital/two dimensional/black and white system of perception/processing/expressing.
Will this system ever be able to see/understand/express the difference between the objective painting and its own product? Of course not. From within the system the result is perfect and factually correct.
Again: is that a problem for the system? No, not at all, and it won´t and can´t ever turn out to be. It serves its own capabilities and needs perfectly. It works, for all fathomable intents and purposes of the system.
Whether the result is successful, useful, working will always be determined by the system, and within and by its paradigms, needs and capabilities.
Is the result objective? Come on!
Does it work? Yes.
Is there a way for the system to understand the difference? No.
(Needless to say that in this analogy the oil painting represents "what is", the camera represents our senses, the computer represents our brain, and the printer represents our communication tools.)