AureliaShipping did have enough going for it to get its own folder for TV Tropes, but only relative compared to other Ash ships during SM. I honestly believe it was a combination of Ash looking more childish (as in, an actual ten-year old), the large cast diluting focus on who to pair Ash with, the emphasis on family matters (really, the only romance was Kukui and Burnet... who also became surrogate parents to Ash), and of course, AmourShipping.

AmourShipping is the ship that sank all ships with Ash, with the exception of Ash x Goh aka JourneyShipping and Ash x Dawn aka Pearlshipping. But JourneyShipping only thrived because Goh was promoted as a co-protagonist and has actually appeared in more episodes in Journey than Ash (to the best of my knowledge). His constant presence alongside Ash allows JourneyShipping to build a lot of ship tease moments and interactions for a fanbase to form around it. As for PearlShipping, the deep friendship Ash and Dawn accumulated over four years is a very big war chest of moments for them. But Ash x Chloe? Yeah, due to a relative lack of interaction plus the fact that Chloe is more comfortable talking to Goh than with Ash, it cannot survive under Amourshipping's shadow.

The reason why AmourShipping spelled the end of shipping Ash with every new girl is because it's the closest canonical ship we could ever get out of the anime. The fact that it was canonical on Serena's end and the fact that Serena actually manages to do the one thing long thought impossible in the anime (Kissing Ash on the lips) is what attracts many fans to this ship to begin with. It's like watching Jurassic Park or Pirates of the Caribbean or Terminator 2. It's so good and top tier that virtually all successors will be seen as inferior, unable to live up to the large impact of these installments.

The only way for any rival Ash ships to get a chance is a large war chest of ship tease moments to rival that of AmourShipping. But it's clear that writers have a favorite for Ash ships. Once Serena is popular with fans, there was no chance for any Poke Girl to become the next big Ash Ship and thus the writers don't bother. Only JourneyShipping managed to thrive mainly because a platonic bromance isn't really seen as LGBT subtext by the writers (even if it's obvious to the audience). Incidentally, it's also why PearlShipping still persisted because Ash and Dawn have such a good platonic relationship that shippers can see the romance subtext even if the writers do not.