I feel like I need to add my two cents to this here. I have 9 characters, 7 of which are children to the other 2, and they are exceptional at what they do. They didn't start out like that though. Yea, they are all incredibly intelligent and wise and soaked up quite a bit of information at a young age due to their mother being a teacher before she retired and their father being an inventor, but they still had their downfalls and their struggles. They didn't even attempt any of the contests or gym challenges or the Alolan trials until they were 18, when they were done with schooling. They just explored as much as they could and caught as many Pokemon (that matched their preferences) as they could so they could learn more about these species and use them effectively between the ages of 11-18. They spent years battling in these schools and soon started their actual journeys around the regions, some of which did so to further their careers and college lessons while others ignored those and just wanted to see how much they can best themselves. It took them a collective of 10-12 years for each kid to get them to this point, making them 28 for one, 29 for two, and 30 for four.
Also, may I add that it takes a good few days to go through one route, mainly because the routes are actually gigantic compared to the scaled down versions in the games. So going through one of the regions will take up to a year if you are gungho about it, or up to 2-3 years if you are really chugging along and enjoying the scenery. In the anime, it was estimated that it took Ash a good 1.5-2 years to get through the Kanto region to obtain all 8 badges (but of course, they kept this hidden and they had to be estimated by what they say or the status of the characters or the passing of time shown in the episodes themselves). Plus, Pokemon's strengths scale like how we scale when we train our bodies. It takes days and weeks to get even strong enough to lift several pounds more with ease, and Pokemon's bodies and minds and elemental powers are much the same. I made my characters either not have the time to challenge the Elite 4 or Champions, or I made them unable to due to their insecurities or fear of losing. And I also made them less likely to even meet such characters as they are super rare to even find just walking about. You'd have to go searching for them or be in an event they would most likely go to in order for them to even see them.
And all 9 of my characters have differences in strengths with their Pokemon and each have their different battle strategies. Some of these trainers follow their Pokemon's preferred battle styles or they have their Pokemon follow their own that is then tweaked a bit depending on the Pokemon they are using. A couple of these people have weaker Pokemon due to their stances on fighting and would prefer to perform or take care of them than cause harm to their friends. Others are stronger and probably would get close to reaching the semifinals of an official league tournament if they even tried.
Games are very unrealistic when it comes to child characters and the scaling of such. Because of the advent of levels and stats in these games as well as the general mechanics of how moves work, they make such unrealistic standards to what would be portrayed in an RP. Don't get me started on the plot points...
The games also give 11-14 year olds Mega Stones before they prove they are worthy enough to even receive such things and are just handed out to further the plot and to introduce the players to the new game mechanics. Plus, these kids are able to take down full crime organizations without much trouble, mainly because the teams don't try and capture them and use Pokemon battles to attempt to control people (look how far that got them). In the anime, it's a bit more realistic, but less so if the Grunts then run away instead of pulling a trap to capture or inhibit the trainer so they can cripple their Pokemon, as well.
The issues with making characters in a universe when it is shown how unrealistic you can make them in the games (and even sometimes the anime) due to wish fulfillment and giving kids empowerment in the games is very prevalent as the line is now blurred between what is realistically acceptable and what is powerful and what is overpowered. Nobody can be like Red or Gold were in the games, or any game protagonist, unless they had someone helping them the entire way throughout their journey. Realistically, Red and Gold would be like they were in the manga, where they are shown to have character development to become as strong as they are now and they also age several years throughout the arcs.
Making a character when all we see are what the games show is extremely difficult to what we should realistically make, and it is what gets some people into trouble here on the site (mainly because they don't read or follow the rules, but also because they think having Key Stones, Mega Stones, and Legendaries/Mythicals are okay due to the games practically giving these rare Dragon Balls and powerful beasts around with hardly a challenge imposed). But also having a character whose 'power level' is on par of a champion they have defeated, and especially so at a young age. It's highly unrealistic. I can see a character training hard for a good year to beat one tough guy in the Elite 4, but all four and the Champion? I would see that being a good several years of training and soul searching before the character can even attempt that.