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.
Several sources as Cook's Illustrated, Alton Brown, and Anita Lo practically insist that you salt steaks before cooking them. I don't think McGee experiments with or discusses exactly when to season/salt a steak in his books, but he has reportedly stated that he is also in favour of pre-salting. The fact that so many people seem to prefer this technique would seem to indicate that there's at least some merit to it, even if the science isn't well-understood.
All of the arguments I've heard against salting steak (or beef in general) before cooking seem to be anecdotal in nature. When pressed for an explanation, many of these people claim that the salt draws out moisture which will subsequently dry out the cut.
In practice, the amount of moisture it draws out is practically negligible unless you actually cure it, which means using lots of salt and letting it sit that way for a long time. I don't know anybody that does this. Well, hardly anybody (warning: do not follow the advice on that page unless you are fully prepared to ruin a perfectly good steak).
When pressed, most of these people (including Anita Lo, above) say that the water it draws out to the surface will inhibit the Maillard Reaction. This is true - the presence of water does inhibit the Maillard reaction and any significant quantity of water will give you a steamed gray steak instead of a delicious seared brown one. But the key word here is significant. No reasonable amount of seasoning will draw out so much moisture that you actually end up with a puddle of boiling water underneath the steak, and even if it did, you would simply pat the steak dry before searing it. You do pat your steaks dry, don't you?
Also note that this applies to dry seasoning. When marinating a cut of beef it is another story entirely. Salt in a marinade really does create brining and that will tend to make the meat juicier. When meat brines, it absorbs extra moisture - the meat still loses moisture when cooked but the added moisture from the brine helps to offset it (this, again, is all in McGee). A saline solution also dissolves a portion of the tougher proteins in the meat, resulting in a more tender result. Salt is a great thing to have in a marinade, which is why some of the simplest of marinades - soy or teriyaki sauce - are so effective. Just, again, make sure to pat that beef dry before pan-searing it if you want to get any sort of browning going on.
Anecdotally - for what little that's worth - I find that there's very little difference in tenderness whether seasoning with salt briefly before or shortly after cooking (before resting). I've done both and I honestly don't think I could identify which was which in a blind test, except perhaps for the consistency of the "crust" that forms when you really pile on the salt - this is a favourable result for many, and I'll often do this if I'm in the mood.
But all in all, the scientific data on this subject is scant; the results are very inconclusive. And it just doesn't matter that much; the debaters seem to put entirely too much emphasis on this point when there are far more important factors in preparing a great steak or roast, such as additional seasonings, what it's seared in, temperature and heat distribution of the pan, and let's not forget the cut and grade of meat. These things have profound effects on the final result, and if I were obsessive about beef to a fault, then I would concentrate my efforts more on finding better quality ingredients and equipment rather than fussing over the salt issue.
Best Answer
Flouring the beef does two things:
In this particular recipe, the flour is the only source of thickening, so it is being used for both purposes, but mostly for the second, where it is essentially creating a roux as your brown the beef, because you are also cooking the flour in the olive oil. In this recipe, omitting it would give you a much thinner sauce.