Biology, I posted an answer that never went through.
Denial of the validity of Torah Sh’Bal Peh is apikorsus. So if someone says, chas v’shalom, that really “an eye for an eye” was literal and Chazal lied and pretended that it means money. That is apikorsus (or meenus).
Criticism of Chazal’s gezeiros and takanos, even attributing to them biases is not apikorsus because it does not deny that those geizeros or takanos are binding. Such criticism does not deny the validity of Torah Sh’Bal Peh.