I have some concerns about your emotional maturity. You seem to be getting very worked up and defensive about every single person not being big on "AmourShipping". It is great you're passionate about it but there is no reason it should make you sad. This is a discussion forum, people will have differing opinions. Earlier in this series, for example, many wanted Ash to get a Skiddo, myself and others didn't. People would provide "evidence" for and against, no problem. Discussion remained civilised (well, as civilised as Internet discussion can).
You like Serena, want her to stay, and want her and Ash to "relate" - fair enough, those are your feelings. Some others don't think that Serena will stay or "relate" with Ash. I notice a lot of "AmourShipping" evidence tends to be either Bulbapedia hints, which are mostly "male character and female character interact somehow", or "YOU CAN'T POSSIBLY ABSOLUTELY 100% KNOW AHHHHHHHHH". Me personally, I don't think that makes the strongest possible argument. The evidence for Serena leaving isn't "100%" either, but historically the only constants in this series are Ash, Pikachu and Team Rocket. The female characters leave and are replaced by a female character relevant to the next game. Of course, the writers could suddenly, after nearly 20 years, decide to make some changes to the series and make it an actual story, as opposed to a means of selling the games, but I feel that makes a better argument. I don't think you can, hand on heart, deny this either.
Ash is a 10 year old boy. I genuinely didn't have any interest in girls etc when I was 10 years old.