Bitcoin will continue to be useful for everyone even if that person is disabled. maybe illiterate people will have difficulty carrying out bitcoin transactions because they are hampered by their ability to see letters and numbers but i am sure that in the future the development of bitcoin wallets will continue to increase and we will see voice-based bitcoin wallets so that anyone and in any condition everyone can do bitcoin transactions easily.
in my country there are still quite a lot of people who are illiterate, but i see that they can still carry out buying/selling transactions well, because there are still many good people who guide them. i am sure this will also happen when transactions with bitcoin are carried out by those who are illiterate.
It is still same thing to me even if a voice base bitcoin wallet is created (even though I don’t think we will get there considering the privacy associated with bitcoin, anything face recognition or voice wouldn’t be welcomed). But still let’s say hypothetically this is created, how does an illiterate person still communicate with the device, remember this are people that can hardly read instructions or even write out anything. First of all they need to able to actually even use the internet which most are definitely finding hard to do, and we all know bitcoin is more complex than that. Have you thought about how they will handle cases like bitcoin transaction needing RBF or them signing from a cold wallet to broadcasting on a watch only wallet. This are cases that hinders an illiterate person venturing into bitcoin. Worst his they trust a friend or family member to do most of this things for them before they get acquainted with it, which is a very big red flag