What do the characters in the game think

I think it's like the anime from their point of view, but with video game rules without being able to see all the video game stuff like stats. I also think that they can see which moves and possibly stats and even less possibly nature and characteristic their Pokémon has. The reason only strong trainers use items is because the average trainer does not know how to tell how much hp their Pokémon has left, and training a Pokémon to use an item or that the items you can use on them aren't scary or harmful is hard, just like it would be to train a real life animal to do things, and the average trainer is also pretty bad at battling and catching Pokémon because most people would be if they had to do it in real life. Aiming at a living thing that can move whenever it wants is hard, and so is remembering all the moves your Pokémon has, same thing for type matchups, also it's tiring for new trainers to shout a move's name and hope the Pokémon know what it means, but strong and experienced trainers can teach their partners how to battle without needing to give voice commands, which makes battling much easier and more effecient. The reason a random ten/eleven year old (you) can become champion is because this is a game to them (or more accurately, you, the player). You can do and see everything with the touch of a button. You can see every statistic like accuracy and EVs and more that they can't. You can calculate everything they would never be able to comprehend, from how likely each ball you have can catch a single mon, to how much damage you can deal with your attacking stats, move power, boosted stats, lowered stats, versus their defensive stats, boosted stats, lowered stats instead of just shouting a word and hoping it can take out their opponent like they do.

This is all headcannon though.