Dracula is not considered a dark theme in Rstudio, at least under Rstudio Server Professional 1.1.383.
rstudioapi::getThemeInfo() $editor [1] "Dracula" $global [1] "Modern" $dark [1] FALSE
(also is there a better place for bug reports alread?)
Yep!
(The link is to the issues page, that just doesn't show up in the preview box).
Ah great I somehow missed this (and apparently google isn't really that aware of it yet)