Accusative is not very useful, except for personal pronouns. And moreover dative could be interesting too in that case.
Regarding the word order in sentence, I think many natural languages manage very well to change it, when necessary (Is it really usefull?) or for stylistic effects (most of the time), without the help of accusative.
IMHO, Esperanto is not easier than English for non-European people, and that's why (among other reasons) it can't yet supplant English as an international language. However, for European people English may be less easy than Esperanto, or preferably than any other constructed language, because of its spelling, some elements of its grammar (irregular verbs, et cetera), and a part of its vocabulary (faux amis and so on).
So we are allowed to reproach similarly both languages (English and Esperanto) in their claim to become 'the' international language. Some others, natural or artificial, could be more suitable...QED