Reagan was intellectually lazy, and he demolished Carter because the debates aren't quiz shows. His "There you go again!" line was devastating. It took a minimal amount of intellectual effort and policy wonkishness to deliver, and it ended Carter's chances for re-election; he was in it up until that debate.
This is very unfair to Reagan as he followed up "there you go again" with a succinct policy justification for the position Carter was critiquing him for. Yes, Trump could have given the same snappy retort and followed it up with something vapid like "I will not dismantle Medicare, I will make it stronger and better than ever before" but to call Reagan intellectually lazy based on this debate answer is quite incorrect. I don't know what more you would ask of him than what he said.
For reference, the exact quote is:
Now whether this is perfectly honest is an entirely different question. After all, those old Reagan records were basically "this bill will takes us down the same path to socialism that the Soviet Union went down."