People who were big into R pre-Tidyverse have this tendency to view the way they manipulated data frames pre-Tidyverse as the "basics," and Tidyverse as the "advanced" method. I think it does anyone learning R for the first time an incredible disservice, for the reason you state: dplyr is fantastic. But the old guard is (rightly) afraid that if people start with dplyr, they'll never get around to learning what base R provides for manipulating data frames. Which is good in my view, and nobody should have to learn that.