I think this reason is very valid. R has warts and issues, but RStudio and Tidyverse authors have shown that R is an expressive language for building coherent DSLs that users love.
R is quite good at developing DSLs (quite Lispy), but Julia is even Lispy-er with a more flexible syntax and unicode identifiers. R, definitely, has a great statistical lineage, but that is also unfortunately what limits it from being as expressive - especially regarding new data types. No one in R creates their own domain-specific data types (that are performant as well) whereas this is the norm for the Julia ecosystem.