so the idea of trying to learn one more is daunting, even if Esperanto is designed to be easy to learn.
Even that would people contest. For me it was easier to learn and I think there things in the language, which make it easier to learn. BUT that idea that it's truly universal "easier" is often criticized and doubted. Which leaves me with a disappointing "maybe" with a slight tilt to "it's easier", so "maybe it's easier?".
I could barely learn a 3rd language (French) so the idea
If we keep in the idea set of how Esperanto came about, then the idea was to learn two to three languages and be a world citizen afterwards. Two languages, because that would be your mother tongue and Esperanto and for three languages that would be your mother tongue, the language of your region like for cultural heritage reasons and Esperanto to be a world citizen.
I learnt Esperanto after i learnt English in school. It's my third language and I belong to those who got afterwards more confident, that I could acquire another language by myself. So for some people it's easier to learn and it brings them then the confidence, that when they find motivation to learn a specific new language, that they could do that.
I myself am still stuck with three languages, because I did not had a strong motivation to learn an additional language. There are too much languages and there are too much conflicting incentives to learn one over another. Wanna understand China? Learn Mandarin! Learn one of the other big languages in the world for financial progress! Then learn Spanish! Be supportive of the deaf community! Then learn one of the many dialects of sign language!
That sounds interesting. Esperanto has no noun-declinations, it's an agglutinating language, you don't bend words (= declination).
But what is barely resembling that what you mention is the two cases of the language, which is nominative and the so called "accusative". Which is adding -n to words to make them an object, depending on whether the verb of the sentence needs one or not. This case also is not just for objects, but also for directions, for measurements and time. That combination normally confuses the heck out of people.
Which is why there is also an in-joke in the Esperanto community "don't forget the accusative", because people forget it or apply it too often.