Why tomatillos matter more than one more spoonful of chipotle
When chicken tinga tastes dull, the problem is usually not that it needs more heat. It is that the sauce base is leaning too far toward sweet roasted tomato without enough acidity to keep the whole pan lively.
Tomatillos solve that fast.
If you already know your household is heat-sensitive, reduce the chipotles first instead of removing the tomatillos. The tomatillos are doing structural work in the sauce, not just adding a background flavor.

