In terms of books that I most come back to think about in terms of its relevance to modern questions is strangely Peasants Into Frenchmen: The Modernization of Rural France, 1870-1914. One of the things that you find in there is this map from p.68 of the edition I was looking at:
What do you find? Much of the population of what is now France didn't speak French as recently as 150 years ago.
In 1863, according to official figures, 8,381 of France's 37,510 communes spoke no French: about a quarter of the country's population. The Ministry of Public Instruction found that 448,328 of the 4,018,427 schoolchildren (ages seven to thirteen) spoke no French at all, and that another 1,490,269 spoke or understood it but could not write it, suggesting an indifferent grasp of the tongue. In 24 of the country's 89 departments, more than half the communes did not speak French, and in six others a significant proportion of the communes were in the same position. In short, French was a foreign language for a substantial number of Frenchmen, including almost half the children who would reach adulthood in the last quarter of the century.
That map is a little similar in concept to one seen in a recent article in Science: AI often mangles African languages. Local scientists and volunteers are taking it back to school
Some of the goals mentioned there seem fairly achievable. For example.
Masakhane’s Decolonize Science project, which Muhammad is also involved in, aims to develop machine translations of African preprint research papers released on AfricArXiv. The preprints are often in English or European languages, but the project plans to translate them into six diverse African languages: isiZulu, Northern Sotho, Yoruba, Hausa, Luganda, and Amharic, together spoken by about 140 million people.
Six languages sounds somewhat achievable, but 2000 languages across the continent and Nigeria showing up as having 520 different languages seems much more difficult to sustain a robust set of resources to support.
In addition it also is much more difficult to provide resources to language communities that are hesitant to trust outsiders and it seems fairly clear that that's the case. For example:
AI RESEARCHERS in the Global South and among Indigenous communities are wary of big tech companies harvesting their data to train proprietary AI models. “Data is the new oil,” Running Wolf says. “And so there’s sort of this very colonial perspective of, this is a land grab,” he says. As a result, many Indigenous communities are crafting protective licensing rules for the data they collect and the AI tools they develop.
Some of these projects are at least hesitantly and cautiously open to sharing due to it's benefits, but I'd still expect the resources available in the less-commonly-spoken languages to be substantially worse than their more-widely-spoken alternatives. As is in Europe I think there are a lot more resources available if you want to learn French or German than Dutch, even though Dutch has an estimated 25-30 million speakers which would give it a population of speakers significantly greater than some of the languages on that Science magazine article's list of "six diverse African languages".
To me rather than a recipe for a robust and thriving economy, trying to maintain full support for a large range of languages, even if some of have only a few native speakers, seems more like a recipes for stagnation.
I've known enough people from Bangladesh to have heard of International Mother Language Day which was adopted by UNESCO and later the UN general assembly to promote multilingualism and linguistic diversity. It's interesting to consider the history behind it in Bangladesh:
In Bangladesh, 21 February (1952) is the anniversary of the day when the Bengalis i.e. Pakistani Bengali Muslims (now Bangladeshi Bengali Muslims) of the Pakistani province of East Bengal (now independent state of Bangladesh) fought for recognition of their Bengali language.
It's one thing for a language with only a few speakers to disappear, but it's another thing for a widely spoken language to be suppressed. How many speakers does Bengali have?
approximately 300 million native speakers and another 50 million as second language speakers, Bengali is the sixth most spoken native language and the seventh most spoken language by the total number of speakers in the world. Bengali is the fifth most spoken Indo-European language.
It's definitely got critical mass with more than twice as many native speakers as all "six diverse African languages" combined and, as such, you probably shouldn't be too surprised that it's survived. In a lot of other cases though trying to support all currently-spoken languages only seems to dilute the support that might otherwise be supplied to those lesser-known-but-still-more-commonly-spoken languages.
Do I think modern France is better off economically for largely being based around a single language? I suspect so.