What did Harris herself say? Not much; she barely had any time.
There was one voice within the Democratic Party whose communication about this was good: Bernie Sanders.
The problem is that people remember the "old" prices, not the "old" paychecks.
It has been said that people see wage increases as something they have a right too (periodically, anyway) but see inflation as something imposed by a 3rd party with bad intent.
When the gaslighting failed to achieve the desired effect (make everyone believe their grocery bill is half of what it actually is) - then they just changed the message to "those darn greedy mega corporations are price gouging you!".
The citizens of this country gave a large middle finger to the gaslighting and bullshittery that was the economic messaging coming from the Biden-Harris administration - and then when Harris failed to enumerate how her administration would be different than the existing one... she was doomed.
It is about the economy.