I could see why you'd say that. Stress creates environments of basic survival, which kills cognitive thought. More immediate survival is more salient.
That being said, if you have access to the internet, you have access to countless free educational tools.
Too much privilege brings sycophantic bubbles of delusion, like billionaires.
Having all the time and money also let's you do a whole thing tank about how to ruin a country to fit your preferences. See the heritage foundation as prime example.
That being said, while it is less easy for the poor, it's still essential to attempt that open mind and learn, so you don't get trapped by a socialized category error applied as fact.
This is where we need predictive processing and the Bayesian brain to understand how beliefs are weighted and compared, and the failure states that might being.
Basically, poor weighting or system communication leads to an over affirmation of something that should have been high uncertainty, if measured from other directions.
Instead of seeing high cognitive dissonance as a sign to align low probability, it gets socialized into acceptance to save the energy of trying to worry about our deal with what, to that system, appears intractable.
DKE is at least useful in framing how each expertise eco-niche is filled with complexity that doesn't Transfer. This is why scientists stict to their expertise, where they have high dimensions of understanding, and low dissonance to uphold.
This can be over-prioritized until no dissonance outside of microscopic niches that act more like data collection than science.
Experts however can work together to find truths that diffuse dissonance generally, to continue building understanding.
If the peasants could socialize that laziness was a lack of meta awareness of the greater dissonance diffusing web of shared expert consensus, instead of laziness being the act of not feeding the socio-economic hierarchy machine, which is famous for maximizing paperclips and crushing orphans.
Pretty sure I got beaten black and blue waiting for library access. Had to protest to keep a library open when I'm gradeschool.
So, growth mindset isn't a privilege, but general access to affordances, pedigree, time, tools, social connections, etc, are all extra hurdles for growth mindset in impoverished places.
If there's no internet access at all, then that's just a disabled system.
Is not static with people, and Issue with growth mindset would just be vulnerability to learning yourself into some information bubble that intentionally cuts off communication, so that you can only use that group as a resource for building your world model, bringing you to where the closed brains go just to save energy, and keeping you there forever.
Groups that are cool with making confident choices fueled by preference in high dissonance spaces. which basically acts like fertile soil for socializing strong cult beliefs and structures.
They also use weird unconscious tools that keep them in the bubble. Listen to almost anyone that's escaped a cult for good elaboration there. Our brains will do a lot to keep us from becoming a social pariah in our given environment we have grown into.