I would disagree with that, using Disneyland as an easy American point of reference three time zones away.
An E Ticket in Adventureland and some more comprehensive theming in Tomorrowland will help (Disneyland's Tomorrowland needs similar help), but that would get Magic Kingdom to about 80% to Disneyland's 100%.
To get Magic Kingdom to 100%, you'd still need to address Magic Kingdom's nearly attraction-less flood control channel known as the Rivers of America.
Getting the Davy Crockett Canoes and Sailing Ship Columbia would be a good start, if not getting the Keelboats back. Whatever you do, get some life and purpose in that river like Disneyland has.
Once the Rivers of America get some of their pep back at Magic Kingdom, you'd need to address the lack of dark rides in Fantasyland. Roger Rabbit's Car Toon Spin, Alice in Wonderland, Pinnochio's Daring Journey, and Mr. Toad's Wild Ride are lacking from the Magic Kingdom. Get some ride vehicles moving in that land. StorybookLand Canal Boats and Casey Jr. Circus Train would be another option for action and movement.
Using Disneyland as the reference again, add an E Ticket to Adventureland (Indiana Jones?) and you are still missing three other E Tickets in the Matterhorn Bobsled, Star Tours and Submarine Voyage.
Kicking out the cash registers and stuffed animals in Magic Kingdom's Main Street Cinema, Fire Station and Penny Arcade would also help. Magic Kingdom's management could visit Disneyland to discover how to theme those facilities to... wait for it... a Cinema, a Fire Station, and a Penny Arcade. An additonal nighttime spectacular as big as Disneyland's Fantasmic! is also a requirement.
Offerings like Fantasmic! and Star Tours exist in other WDW properties, but that doesn't help the capacity and entertainment merit of Magic Kingdom. And that's the point, right?
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Comparing DL and the MK is a bit tough. It will never be necessary to jam as much into the MK as they are forced to at the original park. That wasn't my point. When TL opened at WDW it only has 2 attractions. It felt incomplete because it was. Both TL and FL have always felt half done in many respects. The FLE will fix that for FL. What I'm talking about has nothing to do with the number of attractions and everything to do with a sense of completeness. Look no further then CMM at DAK for a glaring example of what TL was when it first opened at the MK. Incomplete which creates an off-putting disorientation. A land should feel complete even if it is short of attractions. World Showcase feels complete even though it could use more countries/attractions.