My family is very, very fortunate in that we've been to Disney at least once a year since 2008. We are on our 2nd year of APs and plan to renew them in August. We've tried different hotels and eaten at a wide variety of restaurants. Obviously we've found some things we like better than others. Being "frequent" visitors to Disney (I've come to realize within the Disney fan community that frequent is a relative term and for some we go extremely often and for others we are infrequent visitors!

), we have the luxury of saying "We can always do that next time!"
Three weeks before our January Marathon Weekend trip, my parents decided to join us. Months of pre-planning dining reservations were useless because we couldn't add 2 additional diners to our ADRs. Given that my mom is 73 and uses an
ECV and my youngest child is 3 and has mild Cerebral Palsy and the fact that we were now a party of 7, we were not willing to take any chances with just showing up and expecting to be accommodated. We were staying CL at GF and the concierge folks were unable to help us (yes, we paid a pretty penny for our stay). Was I a little frustrated? Yes. My DH was running the half marathon and I was running the full and we had planned pre-race dinners that we thought would be good for our running. Our solution? We simply found alternatives. And our dinner at Bluezoo was the most popular meal of the trip for everyone. Bluezoo was not on my wishlist, especially with 3 young children, but it worked! (My eldest did comment as we rode the monorail through the Contemporary that he missed eating at Chef Mickey. Ok, next time we'll hit it!)
The average Disney guest doesn't know about ADRs or 180 day windows. They don't know if they'll ever be back. They have an overstimulated, whiny, hungry 5 year old crying because s/he wants to eat with Mickey or Cinderella. We all know that they should have planned but, I know from our friends and neighbors who call me before their 1st trip, most people don't understand that Disney is huge and requires planning.
And when you have overtired, overstimulated family members you can have major melt-downs. Trust me, I've been there! My eldest has anxiety and has been known to have major issues during a Disney vacation. We've learned to manage him better to avoid problems but we have many years of Disney experience to draw upon. We also realize that a trip to Disney still is a VACATION and we should treat it as such. When this is your one and only, once in a lifetime trip to Disney, it's harder to keep that in perspective. (Which is NOT to condone rudeness and bad behavior which is NEVER acceptable!) I guess I'm a little more sympathetic to the casual Disney guest who has unexpected mishaps that come from inexperience.

With regards to our January trip... My mom has significant COPD (emphysema) and some cardiac issues that are being monitored. She won't be with us forever. The Good Lord willing we'll have many more years. But we might not. And NOTHING can ruin a trip where my kids can spend time with their grandparents at my favorite place on Earth!
I find the idea that any one thing at Disney is mandatory in order to have an enjoyable trip. But I also think that family vacations are far more stressful than most of us like to admit. Perhaps it's easier to blame Disney. Or the inability to get that coveted dining reservation. We all know people on the boards who save up for years for that Disney trip. They may never have another chance to try CRT. Or at least not when their daughter is in the age group where that would be special. It shouldn't "ruin" the trip but it certainly is reasonable to feel disappointed.
As we start planning our next big trip, I asked my 8 year old why he thinks he tends to get crabby mid-trip and how could we avoid it. He looked at me like I was really stupid. "Too much time together!" And it's hard to blame that on my inability to get an ADR at Le Cellier....
Amanda