Believe it or not, food specificity matters just as much as exercise programming. Both exercise & nutrition need to be customary tailored to the individuals goals, lifestyle, & physiology. 

How do they both drive specific adaptations?

• Exercise programming specificity ensures the right stimulus is applied to get a desired outcome (e.g., hypertrophy, fat loss, endurance, recoup, corrective, strength).
• Nutrition specificity ensures the body has the precise fuel and nutrients to support those adaptations (e.g., muscle repair, energy for training, hormonal balance).

One of the biggest examples I see is training while under-eating protein or calories can severely limit gains, just like following a generic workout plan won't maximize your potential. 

People do respond differently to food. Food sensitivities, metabolism, digestion, preferences, & nutrient timing. Specificity in both areas honors bio-individuality.

Truth is, you cannot out-train a poor diet. You cannot optimize a good diet without pairing the right training regimen with it. 

Your ability to perform in the gym and recover between sessions depends heavily on tailored nutrition—calories, macros, hydration, and micronutrients. A mismatch between training demands and dietary support leads to stagnation or burnout. Just as a cookie-cutter workout plan often fails because it's not sustainable or engaging, so does a generic diet. Specificity increases adherence—because it fits the person, not just the plan.