We walked in the door and the delicious aroma filled the whole house.
This is actually a strong hint as to what might be going wrong. Whenever you smell a delicious aroma during cooking, that's aromatic compounds that would otherwise add lots of flavor being lost to the air. When simmering a sauce, for example, it's not just water that is boiling away. If it was, you wouldn't smell that delicious aroma.
The higher the cooking temperature, the more of these flavorful aromatics will be lost. It's for this reason that many recipes recommend reducing sauces on as low a simmer as possible.
The smaller and lighter those [aromatic] compounds are, the more likely they are to jump out of the pot with the evaporating water and float off into the air.
J. Kenji López-Alt, Ask the Food Lab: Do I Really Need To Reduce Wine Separately?
It seems like the chemistry behind all this isn't really that well understood, but experimenting with two pots (of stock, for example) cooked at different temperatures and tasting the difference proves it to be true.
In summary: try cooking at a slower temperature for longer. An alternative to this would be to use a pressure cooker. The cooking temperature will be higher (thus reducing the length of time needed) but due to the pressure cooker being a sealed container, the aroma compounds aren't lost to the air.