Is the difficulty of Finnish limited to the word length and 25 noun cases?

if you know the noun cases and in which order they go then the problem arises that the best grammar books can't tell you which noun case to use. It's illogical. It is not easy to know when to use nominative, acc. or gen. But it's not that confusing for your Finnish listener to understand you, just a bit confusing sometimes. Main problem is when you listen FInns talk, it does not seem to make any sense, since the language has such difference between formal written language and spoken language and moreover people have different way of thinking and use different style in which they express things. And of course the verbs are a bit difficult, but nothing too much, but definetely more complex than spanish