The importance of musar [books on Torah ethics written during the middle ages] is that without it it is impossible to gain any sort of correct idea of what the values of Torah are. What you get without musar is religious fanaticism or an array of assorted delusions.
The Middle Ages were much more rigorous in defining Torah values.
One reason for this that books of Torah ethics during the middle ages were logically derived from the Oral Law [Talmud] and Written Law. Books that were written later generally are derived from mysticism. some of that might be ok to some degree. But most often it is derived from the teachings of shabtai zvi and Natan the false prophet. I do not like to go into this in detail but the material is readily available to anyone who want to look up the sources.
[Once mysticism gets mixed with Torah, things tend to go downhill. ]
