When my hvac broke and was replaced they put in a 4 inch wide filter box, instead of the 1 inch it was before. They said it allowed 5-10x the amount of air to go through and that seems true. Airflow from the vents is way better and I’ve noticed less dust, plus the filter doesn’t have to be changed as often.
Removing and adding the sheet metal on the intake for the furnace filter isn’t easy, but in case you have the skills or know someone that does it made a huge difference. Or build one of those box fan filters, if you look up Corsi-Rosenthal box you’ll find instructions online.