That is your opinion, and one that I totally disagree with. I loved EPCOT as a small child, a child, an adolescent, a teenager, a young adult, and now an adult. My little brother did too. He loved the Living Seas from the moment it opened (he was 1 when it opened). I took him back to WDW this April for the first time since the Seas was killed by Nemo...and he hated it.
There was plenty to do for kids in EPCOT Center: Imagination and Imageworks, Horizons, World of Motion, The Land, Space Ship Earth, Communicore, Mexico, and many other things that kids could (and did) like. The "Epcot offered nothing for kids before Nemo" argument is a bull argument to justify a totally uncreative overlay to an incredibly creative pavilion. If you mean there were no Disney movie characters stuck in EPCOT rides, you are right. And many of us, even us 1980s kids, didn't miss them.
Those original rides all had the same sort of attractiveness to kids that The Seas has now...but they were creative, fit in the Future World theming, and didnt insult the intelligence of anyone over 3 years old. The original rides were high calibre. The Seas with Nemo and Friends is not, does not fit in EPCOT, is not of the WDI storytelling standards that used to exist.