Also, Esperanto is rather biased towards Indo-European speakers...
It was originally designed by a speaker of several Indo-European tongues for people who already spoke or were being taught Indo-European tongues. The claims of universality came somewhat later.
... and even then most of them would rather prefer to speak English.
Which wasn't yet the case when it was developed.
For a language to flourish a critical mass of people need to speak it.
And there lies our problem.
Zamenhof grew up in Czarist Poland where academics, tradespeople, townspeople, and anyone expecting to move about socially needed to speak or be familiar with multiple languages. He himself grew up in a household which spoke, IIRC, Polish, Yiddish, and Russian as the situation required. His idea seemed like a no-brainer at first; instead of having to learn multiple secondary languages why not have a universal secondary language everyone would know along with their native tongue?
The trouble that Zamenhof never quite realized was that, for it's first adopters, Esperanto wasn't going to be their sole secondary language. Instead, it was going to be yet another secondary language they'd have to lean and, because relatively few people would be using it and little media would be published in it, learning yet another secondary language would provide no immediate benefits.
While the language was relatively simple, the effort to learn it was still more than the immediate benefits learning it produced.
If you have no speakers, you have no language and are left with nothing but a thread on AH.com