SEA will have got the best coaster line-up in Orlando from next week. That counts for something. Brilliant landscaping too, perhaps the best in Orlando. And better animal encounters and enclosures than DAK. That's three saving graces.
SEA failed in developing good rides. The newer offerings of Turtle and Antarctica are rubbish. Of the older ones Atlantis currently seems to be running without effects, while Wild Arctic feels dated compared to all those state-of-the-art screen-based simulators that have sprung up everywhere else.
SEA is a good park, regardless of one's personal opinions about sea mammal captivity. I think your original analogy captured their plight: WDW is unassailable, and SEA got destroyed by UNI for the left-over days.