So the Rabbi disagrees with the Talmudic passage?

1. This is aggadah, and there is no problem disagreeing.
2. This is Rabbi Ishmael’s view. Others disagree with him. In particular, in Maimonides and the Rema (Responsa no. 9) we see that they engaged in this. It is possible, however, that in their view it is indeed permitted to engage in it, but it is not Torah (in the person). But specifically in Maimonides you definitely see that this is Torah. See the Laws of the Foundations of the Torah and the Guide for the Perplexed. “The great matter” is physics (the Account of Creation) and metaphysics (the Account of the Chariot).
3. I mentioned in my remarks that perhaps Rabbi Ishmael was referring specifically to Greek wisdom, which was forbidden (because of an incident that occurred), and not to wisdom in general.

4. And even regarding Greek wisdom, the medieval authorities disagreed about what was forbidden: philosophy, or literature and poetry (the writings of Homer).

What is the definition of aggadah?

I remembered that I once saw an article by Rabbi Lichtenstein where he explained that Greek wisdom is something involving the hand, and has nothing to do with the wisdom we know [if I’m not mistaken].

Whatever is not Jewish law.
As stated, there is a dispute among the medieval authorities on this. Rav Hai Gaon, for example, says that this means the books of Homer and not philosophy.

It seems to me that what Rabbi Lichtenstein wrote stems from the Rivash’s words, that Greek wisdom means riddles and hints that the Greek sages would make through hand movements.

To Rabbi Akiva,
Maybe what he means is the wisdom of demagoguery or rhetoric.

“Maybe what he means is the wisdom of demagoguery” — the Haredim invented that 😁😁