Fat cap necessary ?

45 days should definitely make most all sub-primals more tender, but I hesitate to answer your dryness concern. After all dry aging is a matter or extracting the tasteless water in the meat. With a rib eye at 45 days you should experience about an untrimmed 21% weight (water) loss. My point is if you are comparing a non-aged steak against a 45 day aged one then yes it may seem dry, but that’s the point of a more concentrated beefy taste. OTOH I should ask if you are cooking to time or to temperature? Aged steaks cook faster and can be dried out/over cooked if you cook to time. Ron