I think the big issue is that Harris knows she’s making empty promises and doesn’t like to do that. She also know that the problems were in fact caused by the policies made 4 years ago.

Trump knows he’s making empty promises but doesn’t give a shit as long as it wins him the presidency, he’ll wing it all later, and people won’t remember that he didn’t keep his promises because they only care that he said he would try.

It was something about people remembering how you made them feel, instead of exactly what you did.