>>14
There's no point in no one of them
The exactly same point to mark genitive with 's (like English)
The point: Since of-constructions tend to be very cumbersome, the 's genitive is needed to make sentences sound smoother. "John's mom's boyfriend" is easier and less formal than "The boyfriend of the mom of John". If you've studied other Germanic languages (e.g. Swedish), you can even see that the 's genitives (-s in Swedish) and of-constructions (av in Swedish) have different nuances and are not interchangeable (as they aren't even in English, come to think of it).
Have phonemic tones (like Mandarin)
The point: It disambiguates the vocabulary of a whole language. If Chinese didn't have tones you would quite literally be unable to tell a horse from a toilet brush. And that would make for many an embarrassing situation.
conjugate verbs+substantives (like Russian).
The point: Unlike gendered nouns, verb and noun conjugations contain plenty of relevant information in them. Knowing that a table is a she is not as nearly as important as knowing that this person did that to those. In the case of Russian, noun cases determine the meaning of the individual words in a sentence, and so it is vital to the entire structure of the language.
If we start to point out that this and that grammatical construction doesn't make any sense or "has no point", then we might as well throw even relatively simple grammar out the window, since some languages could do just fine without a lot of the things that are vital to other languages: Japanese and Korean, for example, lack plural markers for inanimate nouns. "What's the use of the plural then? What a stupid construction. Languages work even without it."
Also, none of the grammatical constructions you listed there are hardly comparable to gendered nouns, whose existence really doesn't make a difference, no matter how you look at it. They don't affect the meaning of the words in the language in any way, unlike tones and conjugations and 's genitives.