So I know when I am makiing stir fries if I want lots of sauce I either add lots of different ingredients to build flavors. For example last night I had a sauce with Gochujang, Soy Sauce, Black Vinegar, Roasted sesame seeds oil, chili oil, chili garlic sauce. Each of which was in a smaller quantity but created a spicy and umami flavor that overall covered anything. So try to make multiple flavors together (which is traditional any way). I do love strong flavors so that might not work for you. If that doesn’t work the water + corn starch slurry is a good method to make a sauce thick without adding much flavor.
Tomatoes are the base for most mexican style sauces so add more tomatoes. You can make your own or just use the most mild salsa you can find as a base.