But as it is with any language, programming language, or ecosystem in general: There is strength in numbers. Esperanto is great because it's easy to learn (Europeans have an advantage, ok) and it's the most popular constructed language, meaning there are good resources and actual people (few, ok) to talk to.
Interlingua may be readily intelligible to speakers of Romance languages, but is its grammar any simpler than Esperanto's? Or is comparatively more complex and difficult to learn? Because that's what ultimately matters for the rest of the world's population who do not speak a Romance language.
Interlingua doesn’t claim to serve any community outside European language users, but it does succeed at that, I think.
Overall interlingua is about as simple and regular as can be. A Chinese speaker might still be better off learning English but I can’t imagine they’d find interlingua any harder than any natural language.
Interlingua never cared much about simplicity and regularity and it shows. Occidental before it has something called De Wahl's Rule that is focused on achieving as much regularity as possible while being easy to read at first sight. Here's how it works: https://en.wikipedia.org/wiki/De_Wahl%27s_rule#Rule
If your goal is to hang out with other language geeks, the latter one sounds preferable, but at that point, you may as well be learning Quenya or Klingon.
> if your goal is to convince a few billion people to speak the language
I'd go with English or Chinese.
> If your goal is to hang out with other language geeks, the latter one sounds preferable, but at that point, you may as well be learning Quenya or Klingon.
Esperanto is popular enough that I'll randomly run into Esperantists on a street corner in my city, and I'll get newsletters about local Esperanto events. (And yes, there's a lot of retired people who are into Esperanto because it used to be more popular.) That is literally not happening for Quenya, Klingon, Lojban, Ido, or Interlingua. It may be happening for Toki Pona, but then again, tomo tawa supa mi pi lon sewi li jo e kala linja mute mute.
I'd want to try to learn it again eventually, but I failed miserably the first time.
As an academic curiosity I think it's doing great.