I'm torn. You make good points but, OTOH, if I have nothing else to say, is it really going to hurt to show that I'm paying attention and read the website?
TBH, I REALLY don't think these essays mean nearly as much as we think they do. 20 years ago, I might have paid a consultant for help with everything but nowadays, with all of the information available here and on the rest of the internet, I didn't feel the need. That doesn't mean plenty of people with more money and less confidence don't make a different choice.
The end result is that a lot of people end up with highly polished essays that all look similar, and have little to no original content from the applicants themselves. Adcoms see thousands of them every year. Does anyone who is paying attention really think they are clueless, and that they allow admission decisions to be swayed by essays that they have no assurance are actually written by the applicants themselves?
As a result, I honestly think it all comes down to stats, ECs and interviews. Essays are an exercise we all go through. They give adcoms things to talk to us about on interviews. But I honestly don't think our stories matter that much, nor whether or what we write in the free form field. I have left some blank and written "Why Us" essays in others, depending on the school.
I'm just a first time applicant, and my opinion is based on nothing other than my observations over the past few years. I might be very naive and very wrong, but I refuse to believe that someone who spent $10K for a professionally polished package of essays is going to have a stronger application than someone with objectively more impressive ECs and better stats in more challenging classes, even with half-assed "Why Us" essays in the "Anything Else?" box.
I might never know for sure, since I don't even think my ECs are that strong. I'm doing my best, but I'm not stressing about every character in every essay. I honestly believe the "Anything Else?" box is just a place for us to say whatever we want so that we don't come back later whining because they didn't give us a chance to put something we thought was important in front of them. I just don't think it will tip the scale one way or the other for anyone because, as you said, they already ask for all the things they really care about.