It's not so simple to just say that Magic Kingdom was just a copy and their designs didn't stand the test of time.
As
@GrandCanyonConcourse said, everything built in 1971 was meant to be an improvement of what came before. They didn't "just clone" or purposely make inferior versions of Disneyland rides. Pirates, sure, but that came two years later in 1973.
But a couple of things have happened that have made it easier for this point to be lost to history:
1.) From 1971-1983, Disneyland brought over all of the WDW attraction improvements they could, culminating in the redesign of Fantasyland, but also touching attractions like Jungle Cruise. Even the inferior Florida Pirates introduced Old Bill, who subsequently found his way to DL. Sometimes it is forgotten that these improvements came from WDW and didn't just materialize in the 70s because Imagineering was bored.
2.) At some point, direct clones started being exclusively the Disneyland versions. Tokyo drew its clones almost equally from Magic Kingdom and Disneyland; Paris and the subsequent parks drew almost exclusively from Disneyland (although pointedly not DL's Pooh ride). When it came to Paris in particular, it may have come just as much from who led the overall project (Baxter) and not necessarily as a dismissal of everything Florida did.
3.) The attractions that Disneyland couldn't improve upon due to space, etc. to match improvements of the Florida versions have generally been closed over time (i.e. 20,000 Leagues, Toad). Mansion is about the only one that's left.
4.) Eisner's Disney wanted to puff up Disneyland Paris as the prestigious or artistic or lavish one,
unlike those other ones that came before him where they just copied everything, to make his own accomplishments look better, and with that came the further denigration of Magic Kingdom's accomplishments. It's easy to look at Magic Kingdom's lineup now, or even for much of the nineties, and agree with him, but it's a misleading argument. Disneyland Paris did bring many things to another level, but that doesn't mean that Magic Kingdom brought nothing to the table.
5.) Little information about Walt Disney World's history is available to the public, and Disney isn't doing much to change that.
6.) And, of course, modern WDW is run very incompetently and many people like to view the parks exclusively through presentist eyes.
I'm not sure where Card Walker's Magic Kingdom is coming from, as nothing I have read about the park's history links him directly to the design and construction of Magic Kingdom. Epcot, certainly, but I had always heard the Magic Kingdom directives as coming more from Roy. If there is information about Card's role in the design of Magic Kingdom, I would love to read it up and would appreciate any recommended reading on the topic.
So while I do vastly prefer Disneyland to Magic Kingdom, it's not really accurate to say MK was just a soulless copy. That may be what it is now, but that was never the intention.