@Thorned Rose Ninja  
Different people serve different purposes. I don’t like to over-examine FIM, because frankly everything important that happens has at least a few logic holes because it’s not intended to be a super serious novel or anything. That being said, the point you bring up is actually pretty easily explained with what we’re given.
 
Twilight is well established as a good organizer. Maybe she’s not the PERFECT leader because she’s naive, and often overlooks the obvious like in this image, but she also is great at utilizing the most out of both the tools given to her, and the people under her. At her worst she’s obsessive, but at her best she’s very efficient, and that’s a very powerful quality in a leader.
 
You also have to think about her role specifically. She’s not being geared up to control the sun and moon, and cure everyone’s dreams or any of the other things more unique to the main princesses. (Or at least we’re pretty sure that’s not where the show’s going because that’d be a bit much to swallow imo) She’s the princess of friendship. The very job title implies she needs to rely on the strength of others around her just as much as they rely on her for leadership. On paper, it’s a mutual synergy, to the ponies, it’s the very definition of friendship’s magic. Others give her strength as she gives them hers, and everyone’s insight can have value. So yeah Twilight may be a dunce in some ways, but so long as someone practical like Applejack can be there to make her realize some kind of really basic solution she’s overlooking, it shouldn’t matter.

@Thorned Rose Ninja  
Why not a total nerd, you want someone smart running things do you? That thing you want is someone who is charismatic but is a complete moron

@Goddess Erosia  
Would Twilight make a good advisor then? I find it kind of odd that Princess Celestia would choose a total nerd to be a princess, which requires a certain social acumen. Then again, Twilight has grown in her perceptiveness since season 1.
 
^{Wait, what am I doing? I should be bemused by pony porn!}

Spike: exactly

For you

@Nootnoot  
DID THIS BOOK JUST /ASSUME/ ALL THESE GENDERS?? :v

Did you just assume Spike’s gender, Twilight?

Oh please Twilight. lol Lots of us guys used those female anatomy books in high school as free porn.

@Cheeses  
It’s as soft as Churchill thought italy was.

@Background Pony #A320  

 
O NO

@mjangelvortex  
Gotta watch out for them pimples then.

@StrangeGirl  
Dragon puberty.

Spike is getting older.

Reminds me of when Julian did the cute names for parts of ponies.

@Goddess Erosia  
I’ve known people in real life that were like this too. Very smart regarding school and their jobs, but not so much in regards to some social cues here and there.

You know the best thing is, this is so incredibly canon….  
Twilight’s personality is amusing in that she’s very knowledgeable and she likes to observe the world around her, but all too often she’s a complete moron when it comes to common, practical sense, and she misses the most basic logic that’s in front of her. She would be exactly the kind of “idiot genius” who would honestly not get what she just saw, and after this she’d go back to her telescope or something and perform a bunch of math.
 
There are different kinds of intelligence after all. This is her own special blend - her flaw. And it’s cute.

Twilight, your naiveity is showing.

In the words of the late, great Jiraiya, It’s research.

There are some parts of his education you have been neglecting, Twilight.

If Spike’s puberty strikes, guess it’s time for him to have a dragon to mare talk about the birds and the bees.

Busted.

@Background Pony #A320  

 
I know that their soft underbelly is a weak point

Someday he’s going to have to know this material.

“And it is fictional book anyway. We don’t actually know anything about dragons.”

He’s studying female anatomy for science of course.