It is an amusing thought that if Zamenhof were alive today and he had to take one of the high level KER exams he might not score 100%. Obviously he would fall down on some of the vocab tests and he might not do that well on grammar. I was provoked into thinking this recently by re-reading Lingvaj Respondoj.

Whilst Zamenhof is very sound indeed in his opinions on the evolution of the language, his theoretical analysis of the basic mechanism of the language may not stand up to modern scrutiny.

His biggest mistake here is 'I arranged a complete dismemberment of ideas into independent words.' He compounds his error by listing roots in the UV as though they were words.

Later theorists followed him down the same path by invoking the notion of the inherent grammatical class of a root, but subsequent dictionaries began to actually define words and not roots (ie they defined meanings of root+finaĵo).