When i got the answer for this question i hid, because i didn't needed the answer anymore, but Pokemaster reshow it, thinking about it, even if i don't need it anymore, it can still help other people.
Thing is i moderatly agree with your answer, however i believe that the true answer is because we are limited, expecialy because on Battle tree/tower and alike we can only use three pokémon we have registered before entering the matches, on top of that there are many situations our team cannot properly beat others no matter how good they are, what can we do is only increase our odds of winning like you said, Ev training them, get the pokémon with high IV's, the right nature for his role, also there are things we don't have control over on this kind of games we have no choice but to rely on odds. For example Imagine a fire pokémon with flametrower, the pokémons he can beat in one will not live to retaliate or make use of the opening you gave (keeping him alive), however if they they do resist in most situations a more elaborated npc can make use of your opening or just retaliate and defeat you and the rest of your team in one hit. However if you use the same fire pokémon with moves like fire blast who has 85 base accucary, he will obvious defeat pokémons who he would with flametrower (a weaker fire type move) and will have much more higher chances of defeat the ones who would endure flametrower, but he only has 85 base accuracy, 85 base accuracy is still high, but he will miss sometimes. It means in the end a pokémon with fire blast will have higher odds of make your team win by not giving openings to setups, disruptions or retaliations, however due to his base accuracy he will miss sometimes, when he miss a pokémon who would endure flametrower wouldn't make much difference, but a pokémon who could be defeat in one hit by a weaker move will be there to do what it have to do, but in terms of odds, is much rare for this to happen than fire blast miss, but when it does happen, it is just what it is, we can have control over everything, we can only improve our odds. (Some cases have exceptions)
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(I write very fast and sometimes i accidentaly forgot to type some keys, sometimes i type more and so on, if someone want to edit this comment, is ok but i ask that you only edit the grammal mistakes and nothing more, very often things i put has being edited and endup looking different than what i said, i would rather want my comments hidden than keep them that way, i hope is compreensible, thanks!)
