Story

Esperanto was a good idea at the start, and one that looked-like it could have had a future, for the first few decades. However, since about 1930, it has been very successfully replaced by (multiple) rigidly defined small subsets of English:

https://en.wikipedia.org/wiki/Simple_English_%28disambiguation%29

https://simple.wikipedia.org/wiki/Wikipedia:Basic_English_combined_wordlist

Basic English can be at least as simple as Esperanto, just as fast to learn with as few as 850 root words (Esperanto had 900), Being a defined language these have all the supposed benefits of Esperanto, too: the terms in question being static, not including slang, avoiding complex conjugation rules, etc. Plus simple English has added benefit of allowing you (basic) communication with billions of people, access to untold tomes of information, etc.