Those who say that Ethereum is an alternative crypto currency, are missing the point. However, the distinctions between what constitutes a platform, and what constitutes a currency are not as black-and-white as you describe. One can provide a number of services and applications on top of Bitcoin blockchain, too. The scripting language of Bitcoin is limited compared to the one of Ethereum, but, nevertheless, there is a plethora of apps and services build on top of Bitcoin. And, being publically traded, ETH and ETC are units of exchange, and store of value, so, technically, they are currencies, too.
Nice pile of Polish FIAT currency on the stock photo!