First, let me start by saying that I am not quoting your post to single it out, but, as representative of a number of posts in this particular thread. It's also a revelation. I have felt this way about it for a long time, but, couldn't put it into words.
Basically, there are no 1/2 day parks, there are a lot of 1/2 day visitors though. Again with the $100.00 per day park spiel. Like anyone that doesn't find enough to do to cover a day would actually pay $100.00 to do that park (although it can be justified that there is at least $100.00 worth of entertainment there).
That is not what the vast majority of people are paying. Even DHS can be stretched out over an entire day, easily, if you are not just there for thrill rides. If you are, you must feel silly cause your in the wrong park. Do more research next time! The park you want is up the road about 6 miles.
DHS needs help, it needs attraction that are new and innovative, but, hopefully eventually that will happen, it just isn't happening fast enough for many. My hope is that they take their time and do it right and not just throw something in there to keep the impatient happy.
Although DAK is "notazoo" if you don't like to see animals and learn about them, then this isn't your park. You won't stay any amount of time because once you have ridden Everest and Kali River Rapids... your day is done.
Epcot is really just a shadow of it's former self, but, it still has some very good attractions that are entertaining and interesting (if you are interested in that stuff), if not then you are out of things to do early. I find it impossible to see everything there, stop and smell the roses and get that all done in one day. If I skip half the stuff I can do it, but, one and 1/2 days minimum.
Magic Kingdom I find is a puzzle. There are more things to see and do there now then in 1983 when I first went there. You know what, it took us almost 3 whole days to see everything, so now I can do it in a day, but that is because some of the stuff doesn't interest me, so I skip it now. I want my money back... I used to get three days out of the place, now it's only a day.
So in summary (finally) all of the parks are what we as individuals make them. Some of them are lighter on the ride side, which, if we allow ourselves to admit it, is kind of a blessing. It's a slow down from a hectic previous day and a chance to still be entertained without being beaten. Not everyone is still in their 20's.