@AFresherPerspective it's been close to 2 weeks so I don't know if I remember everything correctly, but here's my take:
I am ok with a slice of life manga. That's fine, but the way they build him like he's really really strong makes it so it's for sure he will battle others. That's the point of strength, he's gonna fight others, but most of them are weaklings.
The problem is...there's no end goal.
If this was a slice of life manga, there wouldn't be much of battles, adventures and such. This would be like that farming Isekai manga.
The MC joined the adventurer's guild. It won't be a slice of life because they made him join a guild that hunts monsters. There will be battles no matter what.
Without conflict, there's no point in battles. We're not even scared at all. We just know: "welp, MC's just gonna beat him" and end scene.
Look at the genres as well. This manga isn't tagged as slice of life, because even the uploader had the wrong idea. This manga covers itself with the facade of being a battle isekai manga, with action, adventure and whatnot, but is actually a slice of life.
Slice of life manga are chill and fun to read. Some manga with action, I really prefer if they would add in some slice of life from time to time, but this...this needs to add conflict.
Even the cliched "I'm an arrogant noble that wants to ruin peasants' life" enemy would be fine if done correctly. The problem is, there are too many pleasantries.
Imagine this like an RPG game, without the final boss, what's the point of the game? There's no satisfying ending.
If this is supposed to be a slice of life. Imagine Animal Crossing, a slice of life-. kind of game, now imagine if the main character, you, have the magic power to summon tornadoes, blizzards, kill dragons. What's the point of that power, if the goal is not to kill in animal crossing?
Usually OP MCs are made for relief. Meaning that no matter how strong enemies are, they will always win and protect the people.
But if there's almost no enemies, there's no point.