We have had a few issues at WDW. That said we've been to WDW hundreds of times. I have had food related illnesses 3 times in my life. 2 of 3 confirmed, the one at WDW, the hospital didn't run the same confirming tests that were run and investigated by the Board of Health like the other two in Illinois and one in Wisconsin. My DS 14 then had a more major food issue at WDW than I did and the stomach damage lasted more than a year to fully heal. The issue I had in Wisconsin, came from butter on table for toast that wasn't kept at proper temp. Likely it went from table to fridge many times over many days. I was so ill I though I was going to die and didn't care.
Until a few years ago the Board of Health reports were easy to find online for WDW. I read them to look for restaurants that had a pattern. Most were ticky tacky infractions, mostly as if the the inspector had to find something. There was one buffet at the time in the WS that kept popping up for temperature being too cold for hot food. We didn't eat there.
When I got really ill it was at a resort, QS, I had a burger that was ready almost immediately. My gut is it had been precooked and was hanging around too long and some cheese plopped on, warmed up and there you have it. Like I said there were not tests to confirm run or follow up from Board of Health.
From the issues we have had I have two pieces of advice. Trust yourself. If something tastes odd or off, don't eat it. Repeat, don't eat it. 2 of the 3 times I've been ill had I listened to myself I would not have eaten the burger and the toast did taste weird. I don't eat butter from most restaurants anymore and I ask for dry toast. I can spot cold hard fresh butter, it is very light in color, it tends to darken the older and longer it has been out. If the buffet food is not HOT, don't eat it. Watch if they take the food from the buffet and replace or if they just keep dumping more and more food on top of uneaten food at buffet. Cafe May had the best practices I've seen, taking away a tray and replacing with new trays. Pecos is pretty good too about keeping things hot on topping bar and removing old trays and replacing with new. Cream that is warm on a table another issue.
For the most part I avoid buffets. Eating at busy times pretty much ensures food is being turned over quickly. For our table service meals we generally try to order from a menu which cuts down the chances of food being old. At the Inn in Mexico I was served a perfectly square portion of fish, that had obviously been kept warm for a long time. We scored a ressie because of guest bolting the park due to heavy rain. Thinking they pre cooked too much and kept it hot under a warmer. It was crunchy and dry. I didn't eat it though I paid dearly for it.