I think it depends on what you are trying to do.
Blaze is very good for smaller to mid tear applications.
React has a bigger community.
Personally I switched to vue because I wanted to use vuetify as a frontend lib. So thats something else you can look into.
I have never used React but I’m going to learn it because you can integrate something like graphql easier and it is not so focused on “meteor only applications” like blaze.
I think blaze can kickstart your application but in the long run you might be better off with react.
So React is something worth learning.
React has a vibrant community with many things already done.
Sorry for my english skills.