I think one huge blunder is ever assigning a static price value to a specific set of menu items. In other words, you don't create a Dollar Menu or a $5 Footlong to try to drum up sales, because you're just going to make these items popular. However, as ingredient prices fluctuate or inflation occurs over time, these items may become too costly to warrant having them. Normally, you can excuse these items for their horrible margins because the point of cheap items is to get people to buy items with better margins in conjunction with the cheap ones. In my experience, most people that ordered from the dollar menu typically stuck to the dollar menu, and that's a problem.
Quarter pounders would come with the fat sizzling on top, not the dried out flavorless "patty" they serve lukewarm nowadays.
It sounds like your food just wasn't that fresh. I haven't worked at McDonald's since I was a teen, but patties were kept in the warmer for... I think 90 minutes? If you got a fresh patty, it was definitely better than ones that had been sitting around, and frankly, it's the manager's job to try to ensure that patties don't sit around for too long.
However, there's an easy way to ensure fresh food at McDonald's... ask for no seasoning. Now, it won't work on the chicken items, because they don't have any, but for a patty, they'll be forced to put one down and
not sprinkle seasoning on it. For french fries, they'll be forced to put a no-salt batch down (no-salt batches have a french fry box left on the handle). The lack of seasoning on the burger shouldn't matter if you have a burger with enough toppings and you can just add salt to your fries.