In my work, and at a more headcanon level at all, I characterize Pokémon as having the three Ss (sentience, sapience, self-awareness) but operating at mostly different scales than humans' do.
They have their own needs, wants and fears, but those are dictated mostly by the morphological "inertia" of their bod structure and evolutive factors and secondly by their individual experiences, in a way which makes so that social interaction with a Trainer (or with humanity in general) boosts self-uplifting at a polynomial or exponential level.
While I do seek out to give something of a scientific explanation to their existence, I don't care to solve technical questions of, for example, if Pokémon are all a sole species or a class / family / clade (how do you clade a candle?) as that IMO lures into dead ends anyway (what sense does it have, if any, to clade together a candle with a physical manifestation of time in dinosaur form?). Instead I plant things in a perspective that there is a scientific explanation as it would be seen in their world, where science does include a factor of what we would consider magic, but that does not mean that this reason behind has to be either known or understood; it is better cast as a safety net that we are safe enough above of that we do not need to observe, but we know it is there.
Of course, there is enough of a magical, or supernatural, element to Pokémon, as that in and of itself is one of the transversal aspects of the franchise (again: candle). But I treat it as being an aspect of their existence sitting together with, and in the same level as, whatever could be perceived as mundane or scientifically-explained about them. My most recent oneshot -Simpler than Magic- for example, makes a point to show that while the abilities we adscribe as "supernatural" for Ho-Oh are mundane to them, that doesn't mean that they can be explained to satisfaction without assuming -trusting- that there is something else going on.
The fact that Pokémon are self-aware but at a different scope than humans also plays an important factor in this. In stories where I focus on Pokémon perspective, the fact that they can feel and use a more "direct" connection to the world than us even if they can't always control it serves to not only place them as more "natural" creatures, but also serves at a meta level to place them as trustable narration tools so that a third party omniscient is properly filtered thanks to their eyes. In Silly human, romance is for Nidoran~ for example, the main characters both have well defined personal wants and they think and act individually, but they do so still at a level that is well integrated with their position as stand-ins for animals: they would find love, they would need to mate, and that means challenges and courtship. In Playfield, while one of the MCs is a wild Pokémon and the other is a trained one, both have shared and explored enough of their particular life experience (chasing after the Sun) that they can think ahead of their own actions in terms such as honor and legacy, not unlike humans aware of human history can.
I think all this was built as an intrinsic property of my view of the Pokémon world and the franchise overall as a place that is intended to be, and defined to function as, a world better than our own, and a world where despite the dangers and the bad things going on, existence and purpose are tied to a sort of meta scale happy ending. Building characters that are their own and that can integrate well with their own world, in a world where this has been for well over millennia, means there is intrinsically no real need for tryhard, "grimdark", "lol realistic Pokémon world is a hellworld" kinds of Pokémon stories. It just doesn't sensibly fit the narrative of what I feel Pokémon as a franchise is about: a world better and more enjoyable than ours.
In the end, it is as well the reason why this all is fanfiction.