The difference between Ripple & other cryptocurrencies such as cryptos based on DPoS protocol is that in Ripple, ONLY institutions can become a "validator" (processor of transactions). Every server processes every transaction according to the same deterministic, known rules. While, for example, in cryptos such as Bitshares (BTS) network ANYONE can become a validator ("witness"). The stakeholders (i.e. BTS holders) can elect any number of witnesses to generate blocks.

If no one mines it then who creates it? If you say its value pegged to national currencies then it should be 1xrp =1usd. If all tokens are already in circulation then "someone" needs to decide/decree on how much to produce or to be in circulation.

As a network it makes sense...as a currency(commodity) it doesn't.

Ripple use case is to move fiat currency seamlessly across borders, so buying ripple is proof of ownership with 1 USD = 1XRP (or weighted rate of the basket of all currencies). There are other cryptos that also offer only proof of ownership but their use cases is more than moving currencies, such as SALT or Steem or ADX