Haunted Mansion and Pirates are world class. Big Thunder is an impeccably done themed mine train coaster that we see done everywhere. No shade, it's one of my favorites, but to a generic tourist, it's just that. Space is a generic tame coaster in the dark that we see replicated a bit. Peter Pan is my least favourite Fantasyland Ride. If they had Alice or Pinocchio or Toad still, you'd have a point, but PPF screams "that's it??" energy.
With Epcot, I get two parks. I get a fun interactive science museum park with some fantastic exhibits, I get Spaceship Earth, one of the best darkrides around today, I get Test Track and a much better generic coaster in the dark with Guardians. I always grab seafood at the restaurant where you get to watch the fish. Soarin' is overrated for me, but people love it so that can be a wash with PPF. Living with the Land, always a fun way to relax for 15 minutes.
Then you got World Showcase!!!! Exhibits and attractions in a ton of well themed pavilions. American Adventure puts Hall of Presidents to shame. Frozen, as a generic tourist. is a much bigger draw than Tiana's. Ratatouille adds a fun trackless darkride (which MK lacks). Then you have incredible restaurants, tons of entertainment, and some of the best views in all of WDW.
Sorry, no way I'd pick MK over Epcot. Even modern Epcot. And, as a tourist, I know HM and Pirates are at a ton of other parks all around the world. I might only visit WDW once, but I may be in a situation to visit another castle park elsewhere, so no rush. Only one place to ride SSE, CR, TT, JIYIwF, LwtL.