The one recent nominee who did engage with the committee on substantive issues was Robert Bork, who is also the one recent nominee to be voted down. The linked article puts it this way:
At the outset of his confirmation hearings, Judge Bork declared, "I cannot, of course, commit myself as to how I might vote on any particular case." But Judge Bork had written and spoken extensively and provocatively on issues like free speech, sex discrimination, "equal protection of the laws," abortion and sexual privacy, and there was no way he could escape questions on such matters. Mr. Specter was especially aggressive in his questions, and Judge Bork often recanted and qualified his controversial views in ways that satisfied no one.There may have been "no way he could escape questions," but he could have used the standard dodge and escaped answers. By answering, he gave the Senators opportunities to make him look bad, and he simply lacked the will or the ability to protect his on-camera image. I'm sure he realized soon enough that deflecting the questions in the usual style would have been the better strategy.
In the aftermath, Judge Bork said that the intense questioning of him on constitutional issues was improper and that the only people who could stand such scrutiny and be confirmed were those with such thin records on constitutional topics that they could duck the questions.Well, if the questions were improper, he didn't have to answer them other than to politely note the impropriety. He chose to debate, and -- I think -- he chose it because he seriously believed he knew constitutional law far better than the Senators. But they knew TV better, and he was pompous and professorial. His belief in his own superiority showed. And people do not like the look of that on television. His notion that only people with thin records can survive the questions is another example of Bork displaying a superior attitude. If he'd just reined in that attitude and "taken the judicial Fifth" like everyone else, he'd have made it.
And now that everyone has his case to study as a cautionary tale, who will ever engage on the substantive issues again? So don't get too excited about what's going to happen at the hearings. They will -- almost surely -- be dull. Unless you find the usual senatorial preening and posturing amusing.