Chicken Casseroles & Bakes: Baked chicken dishes that work use bone-in cuts and enough liquid to braise rather than bake dry. The distinction matters: dry oven heat at 350F for 45 minutes produces dry chicken. Braised at 325F in liquid for 90 minutes produces something different.
Baked vs Braised — What the Chickeeen Bible Says
Most chicken casserole recipes are underdeveloped braises. The Chickeeen standard is to treat the oven as a braising environment: lid on, bone-in cuts, enough liquid, low temperature. The result is falling-apart meat with concentrated sauce.