Air ducts make no sense

Two of the rooms have amazing indoor air temperature control but the air quality in the rest of the house quickly declines

I know that this home has quite an interesting history, but I’m not sure that I’ll ever understand what people were thinking when they were building additions on it. Apparently, it used to be a very small residential house with a single couple living in it. Then, the couple started procreating. Somehow, they popped out five kids and had to fit everyone inside the 1000 square foot home. The only solution was to start expanding the residence to make more space. This is how we wound up with such weird lighting and electrical work, and particularly bad indoor air quality. The original structure of this house was outfitted with a central heating and cooling system that served two of the bedrooms. As the house was continually expanded, the air duct system also had to be extended to bring hot and cold air into the newly furnished spaces. Apparently, this air duct extension and HVAC expansion wasn’t performed by the brightest bulbs in the box. Our air duct system is a nonsensical labyrinth of extraneous ductwork. They extended the air ducts into one room, and later extended the air passageway from that distant point onward. This means, there’s a general funneling effect as far as the indoor air quality as it moves through the air duct maze and into the house. Two of the rooms have amazing indoor air temperature control but the air quality in the rest of the house quickly declines. Whenever the central heating and cooling system is running, there is a drastic temperature gradient from one end of the home to the other. Short of hiring an HVAC company to tear out all of the ductwork and reinstall it for energy efficient air dispersal, I’m not sure what we can do to improve the air quality. Right now, it’s cheaper just to have separate heating and cooling devices in each room.
Air duct cleaning