What's your opinion on Esperanto (language)?
What's your opinion on Esperanto (language)?

Esperanto - Wikipedia

Apparently the language was popular among early 20th century socialist movements because it was of an international character and therefore not associated with any nationality and its use by international socialist organisations wouldn't show favour to any particular country. It was banned in Nazi Germany and other fascist states because of its association with the left wing, with anti-nationalism, and because its creator was Jewish. It has mostly languished since then but still has around 2 million speakers with about 1,000 native speakers.
My opinion is this: who can I speak Esperanto with?
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Exactly.
The problem with Esperanto is that languages don't work like that: they're not created out of thin air. They exist because people speak them and they come into existance from other languages that get distorted beyond recognition by the people who misuse them.
No living language is known to have been conjured into existence, with perhaps the possible exception of a few rare language isolates like Basque that might have been invented from scratch a long time ago, since nobody knows where they come from exactly.
A lot of people actually, around 2 millions on the internet only. More than you can possibly meet in your lifetime, so that's not an issue.
2 million out of 8 billion is kind of an issue.
That's why I want to learn interlingua. It lets you communicate (one way) to most romance language speakers
Interlingua is awesome. See if you can understand this:
Interlingua es un lingua auxiliar international naturalistic basate super le vocabulos commun al major linguas europee e super un grammatica anglo-romance simple, initialmente publicate in 1951 per International Auxiliary Language Association (IALA). Appellate a vices Interlingua de IALA pro distinguer lo del altere usos del parola, illo es le subjecto de iste articulo e le lingua de iste encyclopedia integre.
Honestly Esperanto is fairly readable for romance speakers. Of course Interlingua much more so.
"Misuse" is an inappropriate word to employ here. The correct way to speak a language is the way that others speak the language, so that you are mutually intelligible. Changes to how language is used aren't a deviation from the "correct way" for exactly the reasons you've pointed out: language is not prescribed.
Esperanto, however is explicitly prescriptive. This is because early speakers believed that allowing it to evolve naturally would hinder its ability to be used as an international and universal method of communication, since past writings could end up unintelligible to future readers. For that reason, Esperanto grammar and most of its vocabulary is set in stone. The Declaration of Boulogne states that the definitive reference work for Esperanto is the Fundamento de Esperanto written by L. L. Zamenhof.
I don't think this is a valid linguistic take. There were tons of languages in Europe and Central Asia that are unknown to us. Then the Indo-Europeans expanded and mostly replaced the native linguistic groups. But I think linguists think the critical factor is geographic isolation, for instance Basques and Romanians are geographically isolated, or perhaps I should say geophysically.
This is not the only driving force of language evolution, although is true for imperialist languages like French, Spanish, and English. Languages evolve by generational shifts among native speakers too, eg this has happened with High German, I think.
Europe had non Indo-European languages in it. Maybe Basque is one of the few that survived.
The problem with Esperanto is that languages don’t work like that: they’re not created out of thin air. They exist because people speak them>
This language was spoken by even larger population that said 2 millions but the totalitarian regimes of Second World War persecuted esperantists. So I think that Esperanto bypassed this rule. And fact that after a whole century this language is still alive and has even some native speakers is telling.