It makes perfect sense to say that the target demographic of English is English speakers—or more precisely, the target demographic of Modern English is Middle English speakers who wanted a few simpler rules, some continental vocabulary, following other contemporaneous European languages in not having þ and distinguishing i and j, etc. It was a relatively small change and very intentionally served a community of people who already spoke Middle English well. It was the Python 2-to-3 of English.

The target demographic of Esperanto, meanwhile, was the whole world: people who already had a language, people who already had a workable lingua franca in international contexts (French, later English), and in particular people who weren’t familiar with the European language patterns that Esperanto was largely based on. So it had limited success. A Japanese or Indonesian or Persian or Swahili diplomat not familiar with any European language would be better served learning French or English than Esperanto, because those languages are roughly equally foreign, there are many more resources for learning French or English, there is a larger community and more people to speak to, there is a larger corpus of works, etc. And an Anglophone or Francophone diplomat has very little incentive to learn Esperanto, either.

Modern Hebrew, on the other hand, had a well-identified target demographic: Jews from around the world migrating to the reestablished state of Israel who lacked a shared everyday language. Some liturgical Hebrew was already familiar to most of this population, and there was a strong cultural willingness to see a reestablished Hebrew language. So while it is in many senses a conlang, it was far more successful than Esperanto and now has a large community of native speakers.

So the question of whether a programming language—especially one that is so much like a conlang, not an incremental evolution based on use in practice (like the C standards committee accepting compiler-specific dialectal changes)—has a target demographic is a fair one.