Let's face it, there are some words in English which can't be translated into Esperanto, without using several words. Nor into French, German, nor Chinese. But exactly the same, there are words in Esperanto which can't easily be translated into English. Some of these are very clear and clever words, but they have no easy English equivalent. To us they are useful words, tute naturaj, and often demonstrate the flexibility of Esperanto and its 'esprimivo'.
Try 'Ŝi nedevintus se se ŝi estus kapabla'. She wouldn't have had to if she had been capable, is perhaps the nearest. Then we have 'instruanto' but if that means a teacher, what is 'instruinto'? The translate 'instruonto' and 'instruemulo'. We can use these perfectly naturally in Esperanto, but to translate them is well nigh impossible. Well, not without some circumlocution. 'Instruisto' is a special word.
Yes, 'disappointed' and 'I wish…' are not easy. We have to use more than one word for those. (Remember that 'ŝatus' is NOT 'I wish'!)
I have spent some time finding normal Esperanto words which are pretty well untranslatable, but used naturally. For instance FORTAS (it isn't simply IS forta!), SKRIBATIS, SUBKOMPRENOTA, IMPONAS, PRESTIĜANTA, CELHAVA, PAROLKAPABLA, (?paroliva?), SENAVERTA VOJKURBIĜO, and what about our own special SAMIDEANO?
Think out a few of these for your own use, and you'll soon find that your Esperanto takes on a more interesting feel and you'll enjoy it even more. I'm sure the editor will welcome your lists. I would!