I disagree with you and the parent as to the core issue / cause.
Critical thinking skills generally didn't vanish over the past 5, 10, 20, 30 years. That still exists and you can see it in numerous other topics of discussion that don't get so heated. In some spheres of discourse such skills have been overridden by emotion, feelings, however. People are being taught to suppress rational thought and to unleash emotional reaction instead.
What has happened is a cultural shift in which outrage behavior, reaction-to-whatever, being triggered, feelings-as-all-important, et al. has become acceptable and primary. Virtue signaling - which is a resulting disease of this shift - is omnipresent today. That all started to build notably throughout the prior decade and accelerated during the Trump years. Emotional reaction and how strong that reaction is, became a way to win contests intellectually. This primacy of feelings is now being taught throughout the US at all levels and at all times. It's an intellectual disaster, it turns adults into infants emotionally and intellectually. It stunts their growth mentally and it makes them fragile, weak, unable to partake in rigourous debate without shattering down to emotionally acting out (if you're losing in a debate, throw a culturally potent accusation card to end the debate). For a masterclass in this behavior observe Alexandria Ocasio-Cortez, when she does something stupid or ignorant, or when she is caught lying, and watch how she avoids responsibility (she acts out very emotionally and immediately begins throwing any and all accusation cards to deflect and shut down discussion); or observe her approach to argumentation generally, she always argues from feelings-as-primary (watch how she uses her hands as she speaks, it's a tip-off); she's out on the tip of the intellectual spear for the US cultural implosion and the impending rise of violent tribalism and highly dysfunctional statism in the US culturally (and it's no coincidence she's an avowed Socialist; 20 years from now if you disagree with her emotions, her brown shirts equivalent - Antifa & Co. - will burn your house down; we're nearly at that level of primative cultural behavior now).
People have gradually come to tolerate outrageous emotional behavior. It's conceptually no different than the broken window theory. Bit by bit more and more emotional, acting-out behavior has become tolerated in the culture. Now it's widespread and the US culture is increasingly a cultural ghetto. When feelings become supreme in the intellectual realm, reason and reasonable behavior loses out every time. The culture that behaves that way will collapse rapidly into tribalism and conflict, lacking the approach necessary to resolve intellectual conflict (turning to feelings and emotion as primary can only end in violent conflict in an intellectual contest, there's no way then to determine right from wrong culturally other than who can shriek the loudest or hit the hardest).