As somebody with a JetBrains All Products subscription, I do frequently use the language-specific IDE’s because the IntelliJ module system (read: project structure) can be a chore to deal with when I’m just doing something in Python or Javascript. Having a simplified and focused UI layout and assumptions about internal project structure makes less headache.

Additionally, not ALL of the language-specific IDEs have matching plugins for IDEA (or may be missing some features compared to the standalone build); Rider, CLion, GoLand, and now RustRover simply do not have any way to be installed as a plug-in into IDEA.