What is your definition of "throwing away money"? Is it not using the system to get the maximum benefit out of every credit, or is it literally losing money that I paid? Because after reading this stuff, I went through and quickly chose the restaurants and meals I would eat, and I was about $100 up from what I paid for the meal plan, which seems pretty good.
The other factor to consider is that its A LOT of food. I would assert that most people do not eat an app, entrée, dessert, and alcoholic drink per person at every TS meal in the "real" world. People do it on DxDP because its included, but you are
paying for it to be included. If you do not eat each of those items at all your meals, then you are essentially paying for things you aren't even consuming. Disney prices all dining plans in a way where they will come out ahead most times - they include these items, knowing there will be people who don't eat all that, so they come out ahead. The plans *can* be a discount depending on how and what you eat, but for many people, its simply not cheaper when they are not actually ordering and eating all those meal elements in practice. Had they paid OOP and ordered what they actually ate, it would have cost less. There are also people who still opt for the dining plans anyway because they like the idea of pre-paying for food for convenience and ease of budgeting, which I do understand.
Also, don't forget you will also be paying 18 or 20% gratuity at all meals on top of the plan cost, and with all those meal elements, that can be a large gratuity on the total bill cost. Again, another reason people should really want to eat the way the dining plan allows for, so that items aren't ordered in vain leading to a higher total bill and more gratuity you have to shell out.
Dining plan economics aside, three TS meals each day is also time consuming. Each one can take 60-90 minutes, and you're not always seated on time. It can be challenging to plan FPs or other events around and takes time out of touring the park. Just another factor to consider.
We have done DxDP in the past, and would agree with PPs that the best way to use it is to do a TS breakfast or lunch, and a signature 2TS credit dinner. If you decide to go with 3 TS meals each day anyway, I would highly suggest spacing your meals quite well - again, its a lot of food, and I know the mistake we made is not allowing ourselves enough time to get hungry again before our next meal rolled around. The amount of food on the plan is more than we eat normally at home, so our normal at home meal times ended up not working for us while there. I would suggest an 8am breakfast, 1pm lunch, 8pm dinner - at least. We also found that because we were indulging and trying to enjoy all the meal plan elements, it made us full, uncomfortable, and logy at times. We cancelled at least three reservations because we were not hungry, and sometimes in the heat of the day, eating was the last thing we wanted to do.