Unlike you, I see Esperanto as a remarkable success story. It has survived wars and revolutions and economic crises and continues to attract people to learn and speak it. Esperanto works. I’ve used it in about seventeen countries over recent years. I recommend it to anyone, as a way of making friendly local contacts in other countries.
It depends how you define success. It is indeed a remarkable achievement to have survived this long and have a (growing? I think so) speaker community, and I could agree it is worth learning. But the goal was not to just work, or have a small community of speakers. It aimed to become a world-wide known language for international communication. In this sense, it would need to have an importance of the order English has today to be considered a success, so I think that "not very successful" is even a bit too generous.
