Terminally-Ill Genius Dark Knight - Chapter 30

As much as I like manga, I cant see when people lie to themselves.
And I see this misconception A LOT. Its fine when others think about you better, than you a in reality. But its another matter, when you lie to yourself.
MC, you confusing things. 
You not a genius – you a cheater. Cheater with literal timestop ability.
Unlike everyone else -you havent mastered anything, you have system that masters skills for you. Disregarding this, you have advantage over everyone else, by beating the game 28 times, knowing future events. You basically possess equivalent of occult knowledge about workings of this world.
If you somehow lose the system and all benefits it gave you, will you be able to go toe toe with this world “real geniuses”?. Can you stand against people who dedicated years of their life in single minded pursuit of their craft? I doubt it. Being genius – means that you busted your ass and achieved more than other people. This swordsman, that you killed just now, spent 10 years of his life to master that sword strike. He understands sword better than you ever will.

And the same goes for other issekai protagonists with a system. They may look like geniuses from the perspective of natives of the world, but from the inside? They most often talentless or lazy people, who got power for no reason.
So, MC. You a not a genius, dont kid yourself. 

If you want to see, what real genius in isekai looks like – look at Cid Kageno from Eminence in Shadow. Dude had no system after he isekaed. No one gave him power.
Instead even before the isekai, he himself learned and mastered most of the martial arts in the world, to the point where he could fight swordmasters with a crowbar.
In order to learn magic, he experimented on himself and on the other people. He studied occult, meditations, rituals and other obscure shit. He trained magic control in his sleep.
In order to become “Atomic” he studied nuclear fusion, while most countries dont have nukes, because scientists dont understand process of making them.
He studied art of acting and basically created his own school of it.
He learned to speak multiple languages just to sound cool. He learned write in multiple languages in just to make cool looking cyphers.
And on top of it all, among the other stuff I did not mention – he learned to play the piano.
Imagine doing all that while having no cheat to rely on.