Not entirely true. Here is what is happening, corporate customers prefer often to use React as it is large-team friendly. Many (in fact most) of us still use Blaze.
Blaze will be taken over by the community very soon which will speed up its updates (and there aren't many, it's very mature). Also, React for Meteor is still not a first-class citizen like Blaze, so there are still some rough edges. Finally, know that the community is also contributing to React. MDG is focusing now on the data layer (Apollo). So truth is, the community will be shouldering most of the UI piece.
We are using Blaze and are very comfortable.