"Is it an AI" tests based only on text are pretty silly anyway. There are probably a few billion people alive who can't form complete written sentences. If you have a job, you probably encounter dozens of people a year who can't write coherent emails.
The Turing Test concept appeared when everybody thought intelligence was mostly words, and we could probably easily make computers spit out meaningful sequences of words. Nobody believes intelligence is how well you can write and read anymore (except fad-based media reports "OMG SIRI IZ INTELLUGENT AI SKYNET!"). The Turing Test concept persists because it's simpler than dirt to explain, even though it has never been a valid method of evaluating anything.
I don't think you are being fair on the Turing test, or on the intelligence of its creator.
In describing the setting of the test, Turing first describes an imitation game where a judge must tell apart a man and a woman. He writes "In order that tones of voice may not help the interrogator the answers should be written, or better still, typewritten. The ideal arrangement is to have a teleprinter communicating between the two rooms. Alternatively the question and answers can be repeated by an intermediary." So the text format is out of the practicalities of defining a workable test, not because Turing thought 'intelligence is how well you can write and read'.
Your other objection is that there are humans who can't form written sentences. Well, they could use the intermediary, if they cant write.
But, even if you mean that they can't put a verbal sentence together, the test is framed such that a machine that can pass it can be considered to think, not so that any machine (or human) that can think is supposed to be able to pass the test.
Again, from Turing's paper: "May not machines carry out something which ought to be described as thinking but which is very different from what a man does? This objection is a very strong one, but at least we can say that if, nevertheless, a machine can be constructed to play the imitation game satisfactorily, we need not be troubled by this objection."
In other words, passing the test - succeeding at the imitation game - is designed to be a sufficient test to demonstrate intelligence, but not a necessary one.
You are quite right. Oddly, I think there's a distinction between the mass-media version of what a Turing Test is and the actual imitation game.
Drifting culture impacts what counts as "passing" too. Way Back Then, everything was slightly more formal, proper, and precise. These days, I have SMS chats with some people who rarely reply with more than one or two words (or maybe an emoji if they're feeling really communicative at the moment).
Wow, I didn't intend that at all (and in all three places too, that's quite a failure). Thanks for noticing. Either my fingers are misbehaving or autocorrect needs a bigger dictionary.
The Turing Test concept appeared when everybody thought intelligence was mostly words, and we could probably easily make computers spit out meaningful sequences of words. Nobody believes intelligence is how well you can write and read anymore (except fad-based media reports "OMG SIRI IZ INTELLUGENT AI SKYNET!"). The Turing Test concept persists because it's simpler than dirt to explain, even though it has never been a valid method of evaluating anything.