>>50727657AG wasn't retconned. The concept of the fusion between Ash and Greninja that is the basis of all the transformation is still present. They simply avoided revamping the design because:
1) AG is irrelevant for Journey
2) Ash has a new outfit
Serena still has a crush on Ash and it's clear in the final scene when the ship leaves. The blue ribbon is not present because it was also necessary to visually show her growth. If you had really seen xyz you would have realized that in the end Serena realizes that she has received too much from other people and wants to start giving something to other people in need like her. Showing it without the ribbon shows this side of it. Now she is a person who is able to give something, not to receive it.
But that doesn't mean she no longer has feelings for Ash
