How do humans and yordles face down demons and demi-gods in SR?

Whenever I thought about this idea in the past, I just chalked it up to "video game logic". If you want a wide, diverse, interesting roster of characters, and have an explanation for why they can do the things they do, then you gotta take whats given to you. There are the characters that are straight forward, and then there are those that need a little bit of explaining to understand.

The obvious: Miss Sarah Fortune is a pirate wielding two pistols, so she shoots things. Duh. Lucian wields two pistols as well, and so, he shoots things as well. Of course. Teemo is the spawn of Satan himself, so he haunts and torments you until he finally sucks out and consumes your soul. Naturally.

The not so obvious: Tahm Kench is an entity embodying humanity's greed and gluttony, so he can eat up just about anything. Xerath is an ascended being, bordering on demi-god, so he can shoot giant beams of magical energy. Malphite is an enormous, sapient rock, so he throws rocks at you, ya know, like enormous sapient rocks would do. :P

TL;DR Back on topic. My point is, these descriptions and backgrounds of the champions as well as other lore bits give us reasons for why the champions can do what they do. However, this brings up a glaring issue; how do humans wielding pistols and baby crossbows and a yordle riding on a lizard with a spear take on the demi-gods and demons of this world?

I have a theory on this. Summoners Rift itself levels the playing field. During the process which transports the champions to Summoner's Rift, the super over powered creatures like Tahm Kench, Aatrox, Malphite, and Galio are stripped of their god-like power or immense size, so that the puny little beings wielding their boom sticks and pointy objects have some chance of facing down these beings.

Now, at this point, you're probably saying, "But Flappy, the same thing happens at Howling Abyss and Twisted Tree Line. Are you suggesting that the SAME magic is there too?" Nope, not at all. Summoner's Rift and the battles held there between these champions, are actually mentioned in the lore. So, in this world, these battles between the given roster of champions are supposedly actually happening in Runeterra. On the other hand, Howling Abyss and Twisted Treeline are landmarks, locations that hold significance in this world, but the battles waged in these places didn't involve everyone you can take to fight there. So these battles are works of fiction, what if scenarios, even in universe.

How about it Riot? Am I close? Is there an in universe explanation? Or should we not think to hard about it and simply chalk it up to video logic?