Asklemmy

You need a reason for a large group to choose to maintain a single language over over smaller groups creating their own.

Look at Latin, it stayed mainly cohesive due to the Roman Empire and splintered off as the empire collapsed and the necessity for commoners to maintain communication across thousands of miles dwindled.

English is the current lingua francia because the dominant nation has been speaking English for the past two hundred years and created a pop culture market that is both large and rich, creating a positive feedback loop making the market larger and richer.

For a tiny language, I really like toki pona, but it's meant to be a minimal artistic language, more than an IAL (international auxiliary language).

Last I checked tho, Globasa looks really interesting. The way that they add new vocabulary, and have a good representation of world languages, seems to work well.

Esperanto is also good, but when my partner tried to learn it, they were weirded out by some of it's quirks, like noun declinations based on whether it's a subject or object, that seems unecessary.

Kial ne esperanto?

Because for most of modern history, we were very isolated from the "outside world".

Other than the last 200 years, the best "internet" was a dude on a horse. Since groups of humans developed quite independently of each other, they developed their own languages. However in the modern age this is changing rapidly, with many languages and dialects coalescing into one, consistent, language. Additionally many countries have tons of English speakers which is a defacto "universal language". Most big cities will have english translation for many signs and important documents.

That's not how language or communication work. Humans develop language in real time and in small cohorts. You are lucky if you can understand youth slang by the time you hit 40 and you want to force an artificial lingua franca on four billion people?

Plus, who said language uniformity is a positive? Linguistic diversity is a feature, not a bug. Language is tied to culture, identity and a whole bunch of antrhopological elements. Entire ethnicities are defined by their language. It's bad enough that US cultural imperialism has forced half the planet to watch the same movies and TV shows, why would we do the same with language? If you ask me, there's way too much English out there as it is.

Every time this was attempted we chose the language of the worst colonizer at that time

I really like esperanto as a project: https://en.wikipedia.org/wiki/Esperanto

It had a lot of support with early 20th century anarchists who saw it as a way to make people less nationalistic and prone to their domestic propaganda.

I'd argue that by your own criteria, English is that language.