Because Dawn and May at least were OUTPERFORMED in their first loss as well as multiple other times. Other performers could be legitimately better than them. Serena could only be legitimately defeated by the CHAMPION.
Did you even read what I wrote or are you just ignoring it? She was beaten in the first Tripokalon (Shauna won) and then in the 4th where Jessie won. I'm sorry if you can't accept her Pokemon losing their concentration during the event or performances as ways of losing (calling them flukes, which they aren't), but they still count as I've explained using real-life comparisons. I understand where your coming from, but that didn't happen. You may not like the methods they used for Serena to lose, but they're still legit and she lost.
There were some major flaws though. Firstly, she never faced any real challenges throughout the saga. She decided to cut her hair and start fresh because of a very minor error coupled with rotten luck. It would be meaningful if she showed development post-haircut, but pretty much nothing changed. Her performances were practically identical, there was barely any development shown from her Pokemon training (unless you count Braixen getting a new stick), and she won all her keys because no one else was good. There was no rival who pushed her to her limit (like Paul, who really forced Ash to bring out his absolute best), only Aria defeated her but that is reasonable.
The other main problem I have is her personality. Especially post-haircut, her personality was rather bland, generic and cliché. She could be pretty much described as a "nice and sweet girl who was into cooking and fashion". This makes her character likeable (unlike Iris hehe) but also makes her the blandest out of all the pokegirls. Misty, May, Dawn and Iris were nice too, but they had some real spunk in the sense that they would challenge not only their rivals, but their friends as well. Serena probably had the least chemistry with Ash, it did not feel like they were "buddies", but rather uncomfortable and trying to be polite to each other.
She faced plenty of challenges, just not on the "battlefield" like everyone wanted, which I've already explained. The challenges she faced were mostly mental ones, testing her resilence and will, the same way Ash gets challenged on the battlefield, but in a different sense. The race with her mom was a challenge, her skirt getting ripped and fixing it was a challenge, dealing with Braixen's branch and her attitude was a challenge, dealing with Eevee's shyness, dealing with Ash during the snowball scene where she stood up to him, etc...We get to the Master Class and Serena hurts her wrist and then Palermo tells her to not continue, but she doesn't quit and continues against Palermo's wishes. Even her feelings for Ash was a big challenge and she dealt with it in the end. How many times do I have to explain or repeat myself?
I'm not explaining the haircut again, I did it before here.
http://www.serebiiforums.com/showth...Moments-of-XY(-amp-Z)&p=18261779#post18261779
Her biggest change after it, was her attitude and mindset. Her clothes too of course lol.
As for their chemistry, their characters were portrayed as more mature in this saga, so it was different this time around. Just look at the few private talks they had during the summer camp/river scene, post Master Class, Snowbelle town, their time together in xyz45 and the battle her and Ash had. In the beginning and other episodes Ash taught her things as the other was growing and learning while they both encouraged each other along the way (sounds similar to other sagas with a couple other Pokegirls if you ask me). Just because they didn't battle each other or share a strong rival, doesn't mean they didn't have chemistry.
As for her strategies during the performances, there were subtle changes if you go back and look, but they were the same general concept, I'm not going to agrue that. Blame the lazy writing on that one. We did see her train a few times though.
I mean you're entitled to your opinions about her being bland if you think so (I obviously don't) and other things as well, but some of the stuff I keep seeing is being misconstrued.