I guess if you're dress question isn't focused on modesty, I suppose the only real issue is what style of dress and length? If it's loose/long, it could be annoying getting on/off ride vehicles. Stepping onto almost any ride where you have to step down like Test Track, etc. would be cumbersome. Also would be a pain for a ride like FOP or riding the carousel. And if it's tight/form fitting, with no give, getting on/off these rides would definitely be a problem.
I've watched women in flowy, long dresses about fall on their face because they trip and if it's short and flowy (not loose fitting), it may get annoying blowing around/blowing up all the time. For the most part, what ever you choose to wear, just think what would make your life easier if you were getting on a boat in the water from a dock.
I've worn athletic dresses to the parks that have a built in bra and shorts and those are no different than wearing shorts. I've found them to be the most comfortable. The downfall is similar to wearing a romper since it's a one piece..... so bathroom visits are always a blast LOL. I am not super concerned about modesty....... to a degree, but I do like to be comfortable and prefer to keep my lady bits out of people's faces when I'm at disney. Nobody needs to see anyone's whoha while getting on/off rides.
ETA-
https://thehalara.com/collections/d...ist.1.dresses-skirts-1&pmuih=dresses-skirts-1
this is the type of dress I prefer, the pockets are a game changer too. I have a few from American Eagle also. They're wicking fabric too which is nice in the hotter months.