I actually don't necessarily agree that STEEM by itself is useful. What makes STEEM useful is the ecosystem that STEEMIT create around it that gives its usefulness. One can come up with other unique characteristics that make other alt-coin unique like ADA, XRP, IOTA, etc.
It's the ecosystem. Alone, STEEM would just be one of the coins out there that competes for people attributing value to it. To me, there can be so many supplies out there for other coins that it renders the argument that each coin has a finite supply obsolete.
That said, if we can work hard and make this ecosystem better, STEEMIT won't be just the only manifestation of the usage of STEEM but there will be other real life scenario that can leverage STEEM capabilities.
I listed the characteristics in the post which make STEEM, by itself, better than most other cryptocurrencies. I think we can evaluate things purely within that category. Of course we can also look at the broader ecosystem (and we should), but I still it creates confusion for investors looking just at characteristics they want in a cryptocurrency.