In response to the argument below, the fact of the matter is he is incompetent at teaching.
Let me liken it to something more familiar.
There you are, sitting in your high school advanced algebra class, and the teacher tells you that you can factor polynomials with a degree higher than 2 (yes, just tells you) and then writes a polynomial on the board and then the factored form. No steps or in betweens and expects you to just figure it out. The fact of the matter is, most students can't just figure it out from that and need to be shown the process and will even still have questions. What he did was just do something without precisely explaining the why and how.
For one, the setting is regular high schoolers from Japan being isekai'ed and while we are more 'intelligent (hah)' regarding the situation because we are seeing things from an outsider perspective and have read more manga and thus realize the basic idea of how to fight monsters because of that, they (at least the girls, and this is just the author I don't intend to say anything about genders here) don't know and thus need to have those things explained to them.
With regards to them having op skills, well, actually the MC is basically more op than them, it's pretty obvious, since even the nerds were behind him. Then there's the simple fact that not every one can just 'figure it out.' If you get a new phone, way back when they were new, unless you read the instructions manual (and they don't have one) or ask someone else (said someone else is hardly explaining things like a teacher, and I'm not saying he has to, just that if he did agree to teach he should do it right) then you have to figure it out on your own slowly and they are exploring that and at least trying. The fact is also that they are kids and truthfully, the nerds and MC are the minority representation of kids because video games or not most kids would just starve in the wild because manga and anime, especially ones with actual relevant knowledge regarding survival are less common so again, they are outliers.
Finally, some of the readership is just amazingly toxic. The delinquents are the only frankly negative kids, where the rest are essentially just kids. The fact that people are going on about murdering them for not being hyper competent or getting lucky survival related skills which the MC did (because theirs are only really good for battle until they figure out the nuanced uses) is honestly just annoying. If you're going to argue logic then at least look at it less biasedly.