Ash never getting sought by lower ranked opponents, even through the notifications he gets.
Because it's more rewarding to see Ash battle and defeat people who are higher-ranked and, therefore, have proven strength. But we did see him battle someone who almost certainly had a lower rank than him: Rinto, who had already proven himself to be very strong by defeating him in a battle before.
Ash's every training being the win button he needs to win the next fight he's training for.
You make it sound like he auto-wins the match instantly just because he got a power-up. They didn't grant him instant victory. He still had to work during those matches, even if he was in a much better position with it. The exceptions are Z-Moves and Aura Sphere, and being a climactic move is what they're for. But even then, they were used after Ash brought his enemies down to their last Pokemon through other means.
For example, G-Max put him on par with Marnie's G-Max, all of G-Max Gengar's attacks were deflected or dodged, and Ash had to use the form strategically to weaken Grimmsnarl. The battle actually ended the turn
after G-Max Gengar faded. For Mega Lucario, they had to use it strategically, its attacks were often matched, and the win was heavily attributed to Lucario's resolve.
If the issue is that the power-ups are giving him the edge in the first place, I don't think that's an issue either. There's no point in waiting a bunch of episodes to get pay-off, or having his power-up end up being a damp squib. Also, Ash sought out Mega Evolution specifically to deal with threats in the Ultra Class, including Bea. He intentionally sought it out as a power-up to give him an edge.
Ash never thinking about using his reserves, especially his training Infernape, who was reduced to...a training partner for Gengar.
As much as I wanted reserves, Ash constantly neglects them. This isn't a Journeys thing, but a consistent character trait with him. There are also out-of-story reasons why bringing them on is a bad idea.
Lucario's DBZ Super Saiyan rip-off because OLM was surely denied a chance to get Ash-Lucario.
That's not weird or bad. It's a classic anime trope. And it was used to show off Greninja's legacy and importance, by having it help Ash's current team.
Paul somehow thinking that the PWC is not interesting despite all the world(?) Champions being it it. What more does he want?!
The point was that he grew beyond his goal of trying to be the strongest. He's now in a position where he's more interested in learning about Pokemon and imparting knowledge, so other people can improve. It's a great, mellow goal that shows how much Paul has matured.
He SAID he didn't care about festivities, but the show made it clear that there's more to it. He sought out Oak to learn more about Pokemon, he used his match with Ash to secretly prepare him for the Masters Eight, and IIRC he didn't even mention that he was asked be a Gym Leader. Paul had no interest in spelling out his motivations and instead let his actions speak for him.
The Champion Boogaloo at the Masters 8, when we got not even a single hint three other Champions were bothering.
They don't need foreshadowing because they're already the strongest trainers in their respective regions. Even if they didn't appear, people were able to guess and hope because they were the most logical (and popular) choices. Only Iris and Alain were outliers, but they hinted at Iris appearing again. Alain seems to be there for the shock factor, but XY at least showed Alain likes battling and is one of Ash's strongest opponents.
