The argument may be wrong, but the conclusion
is true: literacy rates
are actually lower in countries with ideographic languages — likely because there are more properties of words in ideographic languages that need to be memorized "literally", and fewer properties that can be intuited, or easily "sketched" verbally in order to ask the real spelling/pronunciation/etc.
One study I recall (on my phone now, will cite later) reported that fewer 20-year-olds have "fluent" levels of reading comprehension for what they read in the [ideographic] newspaper in Japan or China, than in neighbouring countries with alphabetic languages derived from those same historical ideographic roots (Korea, Vietnam, Thailand.)
Another study (will cite later) reported that the reading-comprehension rate for ideograph-heavy works in Japan is also decreasing over time, as more people spend their time reading mostly explicit "[ideograph-]light" novels, rather than literature that would actually teach them kanji. (Which is a vicious cycle.)
Given that ideograph radicals are kind of analogous to alphabetic morphemes, this is kind of surprising. I think it's mostly because it's self-evident how to pronounce alphabetic morphemes if you know the pronunciation rules of the language, while
1. the names for ideographic radicals need to be memorized, more like the names of alphabetic letters (but with there usually being far more radicals in common use per ideographic language, than there are letters in an average alphabet.) And
2. ideograms aren't usually linear, but rather structured (things above/below/beside things, things inside things, things bonded to other things and reduced in the process, etc); and there's no universal cultural fluency for speakers of these languages in an ordering system for spelling out these radicals. You usually have to see a character written before you can truly know how to "spell out" its radicals.
Because of these two problems, you can't just look at an ideograph you don't know, and casually, conversationally spell it out to someone else, in order to ask how it's pronounced / whether you're pronouncing it correctly. Unless, that is, you both know the names of all the involved radicals, and have a good geometric guess for the ordering. In practice, most people don't try to ask this question verbally, but either need to show someone the character written; or need to use a dictionary.
I've noticed that this actually results in distinct approaches to how people treat "literature with words they don't know", between people whose first language is an alphabetic one vs. people whose first language is an alphabetic one. Given an alphabetic-language work with word they don't know, alphabetic-native people seem to be much more confident in just jumping in and looking words up as they go; while ideographic-native people seem to be more reticent. I believe they're subconsciously expecting new [alphabetic] words to be a much larger barrier for them than they actually would be, as they're used to thinking in terms of the barrier that novel ideographs impose.