I don't know much about the state of Disneyland's version, but it may indeed be the case that it needs less work. Prior to its closure, they actually did some maintenance on DL's. At least the animatronics and lighting. Ride system wise i'm less sure about. The MK attraction was in much worse shape when it closed, and the ride system is completely different and a lot more complex (though it did receive a substantial rehab back in 2013). I think MK's is actually classified as something closer to a roller coaster, whereas DL's is more of a traditional log flume.
I do know that DL's version of this Tiana ride is the original vision. MK is a very different layout and had to be adapted after the fact. And perhaps some of those adaptations were a reason why it needed to be closed earlier and perhaps require some additional time. DL's also already takes place in a swampy environment, so perhaps some scenery elements will remain. No clue.
I don't know what Disney was thinking with that wishy washy D23 presentation. The thing is that they ARE allegedly very worried about Epic Universe and are aware that they need to stop behaving like deer in headlights and actually push ambitious new projects. And yet they still don't have any plans for dealing with it. With the DAK/MK plans being just as non-committal as ever, it's clear nothing has been approved and will probably continue to change several more times for several more years before they decide on anything. Or just cancel everything outright. Either way, at this rate Epic will be open long before Disney even breaks ground on anything and is very much expected to substantially tear into at least the non-castle parks...
Will Epic Universe’s impact on WDW be as big a deal as people as making it or will it at worst take one extra day away from the mouse from people who are already on Disney World trips? I suspect that Disneys contingency plan is to just make WDW trips more affordable after Epic Universe opens up.