When we first learn about the concept of case inflections, it is usually said that they allow free word order and fewer prepositions. But sometimes it sounds as misleading advertisement I'm still learning basic Russian, so my perception of the language is certainly limited. Still, I'm not sure if the word order in Russian is much freer than in romance languages, which don't have case inflections at all. As for the prepositions, while genitive and dative are worth one each (and perhaps so is instrumental), you have to know which preposition takes which case (or cases, and with which meaning!). This makes learning prepositions harder. There is also the matter of have irregular declensions, like мост/мосту, or sometimes unpredictable syllable stress shift, like вода/воду. For comparison, when I learned Latin, the case system seemed more useful, because the word order actually seemed pretty loose (but granted, we have no idea how it was with colloquial spoken Latin). Latin prepositions could take the accusative or ablative, which is an extra difficulty, but much less so than the 5 oblique cases in Russian. And some more practical arguments: I'm a bit surprised about the relatively large number of undeclinable nouns in Russian. Do they cause any confusion in practice, or is the context always enough to disambiguate? I suppose they aren't a problem most of the time, or else people would decline/adapt them. I've also seen people here in these forums say that when they read/hear words not declined correctly, usually they can still understand the meaning. That being said, how important is nominal declension in practice?