Because they lost a park classic not just for Pooh, but a version of Pooh that is widely viewed as a lazy, cheap ride that didn't even live up to either of the two versions of it that already existed.
As much as I'm not a fan of the Florida version, it is nonetheless true that even if they didn't want to clone the Tokyo version, they already had a version of Pooh that was fine from WDW that they could have brought over. Of course, it is possible that they had site constraints that prevented them from flat-out duplicating the WDW blueprints that I'm not privy to. But if that is true, or there are other legitimate reasons explaining why the attraction took a different approach at DL, they are underrepported, and so the narrative has become, whether fully accurate or not, that apparently the WDW version just wasn't cheap enough for the DL of the early 2000's, so they had to go and cheapen it more.
Compare the different versions and DL's, charming setting aside, is easily the worst.
Disneyland's:
Walt Disney World's (and HK and SDL):
Tokyo:
While so far as I know he didn't have much of a role in its design/construction/etc., Tony Baxter has talked about how he viewed DL's Pooh as a step backwards in one of the two episodes of the Themed Attractions podcast he appeared on (starts at about 36:00, and while he dances around his true feelings a bit, the implication is clear, and it's hardly a ringing endorsement of the DL attraction or the people responsible for building it):
https://www.themedattraction.com/tony-baxter-interview-pt-1/
If it had to be broken down to one overriding flaw, I'd say it's the cheapness. Say what you will about modern Disney, but other than Pixar Pier, at least their modern attractions don't tend to look insultingly cheap in the way that the Pressler/Harris stuff often did, which certainly included the DL Pooh attraction. If they had even just cloned the WDW version, I don't think DL's Pooh would have quite the reputation that it does.