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.

PyCharm is cheaper than Ultimate, and more focused on Python dev. It's far easier, in my experience to set up PyCharm or GoLand for a Python or Go project than Ultimate.

And yep, can run ancillary plugins to an extent, I don't think you can run, say, the Go plugin in PyCharm, for example, but JS/TS is out of the box IIRC.

Another thing I've noticed is that the IDEA Ultimate plugins tend to lag the features introduced in language specific IDEs for a bit.

JetBrains offer a multi-IDE licence that costs slightly more than Ultimate, worth looking into for polyglot development. But I went for Ultimate for our Python codebase because we're using a lot of FOSS JVM products, and super easy navigation around large JVM codebases to read code to understand some observed behaviour is very much worth it.