If your turkey soup tastes bland, it could be due to underseasoning (i.e. not enough salt), not enough fat, too much unsalted liquid (like no-salt broth or water) and/or a need for stronger or umami flavors. Try adding a splash of soy sauce instead of more salt, plus more pepper and a pinch of chilli flakes to brighten the taste. Turkey has a naturally sweeter flavor and is leaner than other proteins. It therefore needs to be seasoned enthusiastically and have enough fat in the recipe to taste really savory and delicious.