To get more flavor out of cumin, you can use whole seeds, and toast them briefly in a pan before grinding. If you don't want to put forth that extra effort, you'll just need to add more cumin. If it's not salty enough, the best solution is to just add more salt (sorry). Salt will enhance the other flavors as well. A bit of cornstarch would help make the spices stick, and dry out the mixture. I'm not sure how much water and vinegar you're adding, but you may just be watering down your beef too much. I usually add just enough to keep the spices from sticking to the pan, but not so much that there is a lot of extra liquid that needs to be reduced.
Your spice mixtures may also contain some form of MSG. You can get a similar umami "punch" by adding a dash of Worcestershire sauce.
Edit: I don't know how I missed this, but the other answers point out the lack of garlic and onion. Your store-bought spice mixtures definitely contain plenty of those in powdered form, which you can use, but fresh is tasty too. Don't add fresh garlic too early, as it can easily burn and turn bitter.
As someone who has raised beef cattle (here in Oklahoma) I must say the TFD is (unfortunately) mistaken, (at least here in the U.S.) Most cattle fall into one of two varieties, Beef and Dairy (there are also some breeds that are almost exclusively show cattle) The most popular (and common) Beef varieties are Angus, Limousine, Herefords, Longhorn; This list, including cross breeds (for instance, limangus, what I raise, is a cross of limousine and angus) and constitutes somewhere around 90% of beef production with in the US. (not include 'beef' used for things like dog food). I would consider that list to be in descending order of beef quality (but that is a matter of opinion...)
There are several varieties of cattle which are raised for dairy production, and these do not generally produce quality cuts of meat, but do produce copious quantities of milk. These breeds are led by Holstein-Friesian, Brown Swiss, Guernsey, Ayrshire, Jersey, and Milking Shorthorn.
Buffalo (or Bison) is a separate breed altogether and is no longer all that exotic. I regularly use bison to make chili.
Yes, cows are 'females' but not all cows are heifers, a heifer is a female that has not yet given birth to her first calf .
And @Scivitri while feeding and ranging cattle do make a difference the driving force in beef flavor is still the breed. I can tell the difference between breeds by flavor but the difference from feeding and ranging is really more about tenderness and texture.
Best Answer
Whether or not it's a good idea is subjective, but the Chinese seem to break that rule a lot! For example, Northeastern Chinese sweet and sour pork (guō bāo ròu) is characterized by an intense ginger flavor. The Sichuan classic twice cooked pork (huí guō ròu) calls for boiling the pork with ginger. A common condiment for beef dishes/sauces is black bean garlic paste (蒜蓉豆豉酱). Perhaps this saying is associated with a specific Chinese regional cuisine?