Hollow core interior doors have a honeycomb of cardboard between the skins. You can't really fill them. Most of the sound travels through gaps. If you don't believe me, go out to your car, get in, roll the window down 1/8th inch and listen. Then roll it up tight. With the engine off, of course.
Laundry room noise can be transferred to the floor and walls too. See how much noise can be stopped with some towels stuffed under the door before doing anything else. Then consider placing the washer and dryer on rubber pads unless you have a slab house.
I turn the valve at the wall for the toilet down to the lowest noise level. It takes a little longer to fill the tank, but it's quiet. It doesn't take that long to fill 1.6 gal anyway. That trick might help with laundry noise as well.