Sautéing and stewing is more about feel and taste than necessarily accurate temperature, but when you use your oven to cook, you depend on precision. An oven set to a specific temperature allows you to correctly estimate when that chicken is going to come out perfectly cooked and juicy instead of horribly dry or horrifyingly undercooked.
If your oven is sending out undercooked food, a little investigation may find that the display is lying to you. It may say the oven has heated to a perfect 350, but your tests show that it is only about 200 degrees
A simple fix is opening your oven up, locating the temperature sensor in the back and seeing if it is touching any part of the interior of your oven. Your oven’s temperature sensor is located in the back and it looks very much like an unassuming metal prong just poking out into the air. Rather, that is what the temperature sensor should look like. If it is bent down, or worse, broken off, then it needs to be replaced
However, if the temperature sensor is jutting out and doesn’t look bent or damaged in any way, this means that it could very well be faulty. It is recommended that instead of just blindly replacing it; you test the temperature sensor with a multimeter for continuity.