I don't think anyone is objecting to people who carefully run the numbers on
free dining and determine they come out ahead. For large families in moderately priced rooms, it can be a killer deal.
It's the people who go the dining plan route because of "convenience" or "budgeting" reasons, or because they don't want to think about what they're paying while on vacation. In many of those cases, they're often not actually saving money. I (and many others) see that as poor monetary planning - you're basically giving Disney extra money to avoid thinking about giving them money.
Outside the parks, a good comparison is credit card usage. Many people don't use credit cards because they don't trust themselves to use them responsibly... but that strategy is in itself irresponsible. Used correctly, a good rewards card is a much, much smarter choice than a debit card or cash - you can get paid 1-2% on all your purchases, you don't have to pay for almost a month so your money keeps earning interest in your bank account longer, and you're protected much better against fraud since your own money isn't at stake. If you pay your bill in full every time, you never pay interest at all - yet you're improving your credit score every month as you make your everyday purchases. The only time I ever use a debit card is at an ATM to withdraw cash...
Take a few minutes to add up what you are likely to eat during your trip. If the numbers work out well in favor of your family with free dining, by all means take advantage of it. But make sure you run the numbers first with a critical eye - if you're an adult couple staying in a Deluxe, for example, it's very unlikely to work in your favor. If taking a room discount instead is a wash or a better deal, it can actually make your vacation less stressful to pay cash because you don't feel obligated to use up all your entitlements.
If dining sounds attractive because you can eat what you want without worrying about cost - but the calculators say paying cash is a better deal - how about putting the money you would have paid for the dining plan and tips on a Disney gift card? Bring that with you and use it to pay for all your meals - heck, put a label on it and write Dining Plan, then tell yourself you now have a dining plan

. You'll have the same relaxed vacation, total flexibility about where and when you eat - and a surprise amount left over at the end to buy some souvenirs to take home with what you saved.