Human beings don't do a good job of "observing" the universe either. Our senses and our minds are adapted to life at one and only one particular scale, and at only a small range of EM frequencies and sound wave frequencies, and at a very idiosyncratic experience of the passage of time (in spite of the sophistication of some of our highfalutin scientific equations, which in any case are not true "knowledge," nor are they the common property of all human beings). Other kinds of animals are far superior to human beings at observing other aspects of the universe, which must remain quite beyond our comprehension and even our imagining.

As for Plato, inasmuch as he was a child of his time, he gets caught up in a lot of passing interests and suppositions which a Platonist "after a fashion" such as myself has no need to commit himself to. What's essential remains as true as ever.