I have had good luck in the past using free reservation finders (touringplans.com has one and I know there are others.) They will text you when a reservation opens up at the location and time you prefer. But back in the pre-COVID days people were constantly shuffling which park they would attend, which fast passes to use, etc. so dining reservations changed all the time, especially the day before the date you wanted. I’m not sure how much shuffling happens these days.