I think the problem is in the anime Ash is an Audience Surrogate Vanilla Protagonist for the target audience (children) and thus isn't allowed to grow up. He's never really allowed to be fleshed out because the anime's main focus is on the Pokemon and showcasing all the new ones each week or other features of the games.
At the core Ash is a character archetype. The Hot-Blooded Nice Guy Kid Hero / Idiot Hero. Having him suddenly kicking puppies would be OOC of him.
Having recently took part in NaNoWriMo when discussing characters its important they have multiple hobbies, interests, likes/dislikes, goals, quirks, etc. that can be layered onto them making them more complex and unique. Some ideas I have include:
1. Ash is a surprisingly good singer and likes songs that get him Hot-Blooded and enjoys playing video games.
2. Ash is a fan of Sun Tzu's Art of War (he once gave Brock the 'know yourself, know your enemy' quote way back in the day) and does his best to apply those teachings in how he battles and how he trains his Pokemon. However Ash is still very much the ditzy Socially Awkward Hero outside of battles. In battles he's pretty much the most friendly Blood Knight you could imagine. He loves to battle. Winning or losing doesn't matter to him as long as he and his Pokemon enjoyed themselves.
3. With his father absent for most of his life. I'll give him issues there in the 'mad at him for abandoning him and his mother' sense. One of his goals is to find him and kick is ass. This is why he hates people who abandon their Pokemon because while his mother might put on all smiles for him when he brings up his father that doesn't stop him from hearing her sometimes crying at night… Thus Ash is very much a Father to His Men (going back to Sun Tzu again) and views his Pokemon as his family.
4. When puberty hits, he'll show attraction to girls (like blushing and getting flustered and give us the occasional "she's cute"), but his main focus is on his goal to be Pokemon Master so he doesn't really bother with romantic pursuits. It's just not a priority at the moment.
edited 10th Jan '16 11:36:53 PM by WorldTurtle2
That's all pretty good.
Symbiosis had a really interesting AU twist on Ash and most of the other anime characters in general. They were still recognizable despite those twists.
Jessie and James were really disturbing examples of that in that AU....