It was ahead of its time, perhaps. I never heard of it until this thread. It would good to learn from its failure and not repeat the same mistake. But certainly just because something did not succeed does not mean another solution won't.

True, it does not mean another solution won't - but what is there to suggest another solution will do any differently?

None of these alternatives: http://en.wikipedia.org/wiki/List_of_constructed_languages have spread even as far as Esperanto. Whatever Esperanto did, it did something right.

(And the way you say "learn from its failure" - it's still around and widespread on the internet and available in Apps; you can learn it from http://www.kurso.com.br/ and http://www.lernu.net and talk about it at http://www.reddit.com/r/esperanto and write in it at http://www.reddit.com/r/esperante and chat in it on IRC on Freenode, or verbally with Mumble http://retbabilejo.net/ , there are decks on Memrise for it, it's in development on Duolingo http://incubator.duolingo.com/courses/eo/en/status and there are Facebook and Skype groups, Anki flashcard decks https://ankiweb.net/shared/decks/esperanto and heaps of Youtube videos in / about it https://www.youtube.com/results?search_query=esperanto ) and yet it still isn't very popular (despite the Internet), and you still had not heard of it. That's a failure of it.

I think it's more likely that most people don't want to invest thousands of hours of effort into learning another language, and those who do, do so because they like a particular country/language/culture, than any big mistake it made.