There’s plenty enough to do at every park for a full day, but there also isn’t, if that makes sense lol. MK I could spend park open to park close without hesitation, but as someone that has been to these parks so many times, I know how to navigate the parks to get the most out of a day from multiple parks that wont have me standing in the middle of the park midway through the day questioning what we want to do next.
If I’m at DHS and there’s a long line at ToT, ill just walk over to EPCOT, grab something to eat, take a walk around WS and then walk back to DHS when I see the lines have gone down a little bit. Sure, in the time that I walked to and from EPCOT I probably would have gotten on ToT, but sometimes that walk over to the other park gives me a nice breather from the crowds and parks in general, and I find it relaxing to walk around the boardwalk, until I hit the vacation killing fence, of course