To be fair, twilight i think everyone knows, is smart.
But, ponies/Equestria in general possibly not that much.
How many of them have any idea how their machines work?
Most machines seem to run on magic.
And magic seems to work on anything without any conditions or problems.
So Magic is not that similar to electricity, electricity needs wires and circuits, it needs switches and computers to manage it.
Magic, just works.
It's possible the main 6 to be somewhere between high school and young adult (mid 20's?) education?
Not to mention I know most people ignore the show was made for under 18 and more for 16/13 or younger teens/kids
So, there is not real complexity to stuff.
And stuff is pretty simple.
And the ponies are made to be at that 13 or slightly older mental level too.
But "smart and mature" 13.
With the rights/powers of adults.
It's not like any of main 6 got in a serious relationship. (as long as you don't count non cannon last season)
Most people above 16/18 have had a relationship. (aside from people on this board.)
The point is, I think it's fair to say that twilight is smart for ponies, and ponies aren't that smart.
Equestria is like Europe in middle ages, with middle age education (dumb, and not advanced), but with magic to help make some modern stuff like trains and stuff.