I think that's the "Achilles Heel" of any script, as you pointed out. I know what a carburetor is, but I have no clue what an advance-retard control does. Anyway, before the end of WWII the Japanese used traditional forms of kanji. The kanji they use nowadays is simplified, in some cases so much so that the original character cannot be infered from the newer one. For instance, (old form on the left) 體=体 and 會=会. I'm guessing that's the reason it was hard to read. At any rate words in any language become obsolete, so I don't think it's a kanji-specific deficiency, if you can call it that.