Since STEEM did not get an A or even a B+, there must be something that got under the skin of the people who did this rating.
What might have cost STEEM a better grade is its limited use for most noobs, outside of HODL.
Even if it is listed on various exchanges, in most cases, it is just a rock in the water. It is not functional for trading for one reason or other. Either the exchange is down for maintenance for weeks, as with OL,
and/or
not receiving new members, as with Bittrex, et al.
The future of Steem can be pep-rallied; but, until it reaches a level of functioning the top cryptos present, the grade of B- is somewhat generous imho.
Peace.