@Nessen Okay, now we're talking.
First, agriculture revolution. First I'd think is crop rotation. Possibly didn't exist in that world yet, easy to implement. Also, agricultural improvements (the ones we learn in grade school, I can't be bothered to look for the English names, I studied them in Spanish. But you know what I'm talking about. The "watering drip" thing whatever using pipes, that saves water instead of you having to go manually water all the crops, for example).
How do you call the mix of all of them? "Agricultural revolution". Could the author have explained every single one of them? Yes. Would everyone complain about how he explains every little thing? Also yes.
Can't make everyone happy. I for one was pretty bored when he explained the whole sewage thing, I just skipped those 2 pages.
Could he find a balance? Hopefully, if he's a good writer, which he's not. He's better than most, but not "good". Or rather, not good by the standards you're trying to apply, which I think are geared more towards literature (actual books) than manga. For a manga, I think it's way more than decent.
As for the speech... I want to agree with you, in a way, but I can't. For several reasons.
One: suspension of disbelief. The author wants to create a situation where the MC is a good guy and good leader and people follow him, so he gives a motivational speech, people are moved, things get better. Is it wishful thinking? Yes. Is it realistic? No. That's why it's called "suspension of disbelief".
Second: Have you ever, and I mean, EVER gone to a political speech? Do you know what fallacies are? Politicians use them every other word. I'm going to give you an example, and I SHIT YOU NOT it's true. There was a political rally in the city next to mine. Let's call it "Madrid" (cause capital of Spain, whatever). The politician LITERALLY said "CAUSE THE PEOPLE OF MADRID, ARE THE PEOPLE OF MADRID!!!!!!!".
People lost their shit, hands were clapped raw, panties were wetted and dropped... The politician won the elections.
See, this is something that I've wanted to comment for a long time in MANY mangas. Some of the commenters ARE right. You guys say something like "this makes no sense", but you don't seem to realize that people MAKE NO SENSE! We have flat Earthers! We have anti maskers! WE HAVE ANTI VAXXERS FFS!
Why are you trying to make a faceless mob smart and intelligent (especially when the literacy rate is fucking low, which means they're probably moved by emotions) when irl people are generally NOT smart and intelligent?