a. Flu is in droplets....COVID is partially aerosolized we know now. Masks probably do a better job of stopping the flu as a result than COVID.
b. For the same reason distancing helps. The distances for droplet transmission are smaller than aerosolized
c. The biggest change in culture has been if you feel sick stay home. In the past I've caught flu from colleagues coming into work sick because of presenteeism (e.g. it's the flu...no big deal), kids being dropped off at school sick because parents have to work, on an airline flight from someone sick of the flu sitting right next to me
d. Most kids were out of school. Flu hits kids harder and the schools are a breeding ground for flu. Now, even if the kids are back in school their temp is being taken and they wear masks.
That said, given flu hits the young and elderly particularly hard, one thing I think we should keep is stay home (and keep your kids home) if you are sick....drop the masks, distancing, and mass testing. Maybe during a hard flu season introduce back in temp screenings at schools but that's really as far as I'd go. Viruses are part of our life. They are part of human history.