It's no myth..
Let's debunk your debunking... You suggest calling 'EPCOT outdated' a myth and support your POV by outlining how the premise and theme of the classic rides were still relevant, and blame lack of 'care' (as a wide catch-all for lack of refreshes) and later Eisner initiatives for the destruction of things you claim were salvagable.
But here is how your argument falls down. You never address the actual ATTRACTION as being dated or not...
Your entire punch line is a nitpick that play out like a fanboi love letter instead of facing the actual world and customer of the time.
instead of looking at the attraction presentation, it's format, it's tech, it's style, etc.. you use a generalization that your 'care' category could have somehow kept the attractions relevant like IASW or pirates have been... yet fail to dig into WHY those AA attractions are able to stay interesting to modern audiences while other AA heavy attractions quickly needed saving as the world around them changed.
Rather than acknowledge those rides were in desperate need of overhauls.. you focus on a point of 'the premise is still relevant, so we must call the idea of them being outdated a myth'. A ride that is desperately in need of a refresh and rework is still outdated, even if you still kept the attraction concept the same (like SSE).
FutureWorld even when new, was heavily criticized for elements like the repetition of the show format - and as you acknowledge, WoM and SSE hid it the least. Most of these shows that didn't survive all carried this same narrated slow moving history lesson format. Once the awe factor is removed... that common thread becomes a weakness because simply put... how many of the same thing could guests appreciate? That's why the format can survive in SSE, because it's largely on it's own now, instead of having 4 more of it all around it grating people down.
You completely miss the entire society topic as well... probably because you didn't actually experienced any of these attractions or the time frame, did you? The tone and how people were addressed was changing rapidly.. no more droning stiff collars, we were moving towards the Rad 90s. The narration and format felt dull and flat vs everything else that was emerging at the time. Living Seas and UoE were the worst in terms of feeling more like a 1984 reading... than entertainment.
The show tech itself... no more was just spinning silhouettes going to cut it. The film elements in all of the classic attractions really stood out as dated and stale. Every representation of what contemporary felt more 70s, than 80s and into the 90s. It felt more Disco->Syn Pop... and less futuristic. 1983 Tron graphics didn't inspire people anymore. AA figures needed advancement and lagged the newer innovations.
Early EPCOT Future World was able to wow everyone with scale and new. But by the late 80s.. the new was gone, the settings all felt woefully dated to society, the futurism was dated and not in sync with culture of the time.
As fans we all love Future World for it's ambition, it's scale, it's setting, it's uniqueness, and the work of some of the most famous imagineers. These things are all great. But they don't counter act many of the realities that matter to the gen pop that the parks rely on.
So yes, you are correct the themes behind the pavilions like Communications, Transportation, Energy, etc were not outdated - but that doesn't mean the attractions themselves at the time were not. And even if you say "well they just had to update them" -- Yes, that's exactly it.. they needed major overhauls of all major portions, story, tech, and style.. and that's why they were in fact outdated by the early 90s.
Arguing over how they could have been saved vs replaced, is a different argument... but doesn't negate that the pavilions were all due and their late 70s and early 80s look, tone, and tech were all hanging out as stale. So no, it's NOT a myth that Future World was outdated.