I think the main reason so many in Paris were hesitant to embrace the "kawaii" fashion show is because the translation isn't quite appropriate. Cute and "kawaii" are definitely not the same thing- there are some similarities, but also a lot of differences! As you noted, kawaii in Japan is for all ages, and as is clear in the show, "kawaii" designs are actually quite innovative and can be very sophisticated.
The word "cute," however, is typically associated with childish and silly aesthetics, and does not lend itself to the level of innovation, seriousness, and sophistication that is carried with all things kawaii. I bet that if people were presented with the fashion show with a more appropriate translation, they would be much more excited about it. After all, designers from all over the world will go to Japan for inspiration!