Exactly. That's why it's so hard to budge.
You are familiar with my posts. I do not blithely post "S is stupid" sentiments.
Everyone has limitations, what differs is how those limitations apply.
S types that I know are definitely not stupid, but they can be very very literal. As long as I stay with in very literal constraints, I can talk about very complicated things with Si types. Once I start going into my more native Ni-style hand-wavy explanations, communication falters. It's how I can tell who is what type, based on what particular communication style I need to adopt to communicate clearly.
Si types can have a "very very big box", if you will, and be experts and even masters of their particular intellectual domain. But due to being concrete, that domain is static, and it's difficult to introduce new ideas that don't fit into that domain.
There is NOTHING wrong with that. It has strengths and weaknesses, but there is nothing wrong, and these kinds of experts are essential to our society. They're also mostly invisible: the kind of people who understand how engines work, or sewers work, and keep track of all the details that keep us from dying due to engines exploding or water being contaminated.
Ni types tend to be experts in more abstract domains (like math and physics), instead of concrete domains. General principles that work universally, not concrete things like engines and sewers that have lots of specific details that, if ignored, result in very bad things happening. Each has their strengths and weaknesses.
When I offer vague generalities such as "inside the box" and "outside the box", I'm not positing "stupid" vs "smart" but one set of strengths/weaknesses vs another.