For two of my my recent solo days, I went to Hollywood Studios, getting up super early to get a boarding group for Rise of the Resistance. I’m not a Star Wars fan, but I loved it. Then I rode other rides, took a break, then rode again later in the evening and went to Fantasmic! one time, and rode with no wait on the Toy Story rides until park close.
I love Epcot as well, and that’s a good one for a solo trip.