With same languages? Whenever I stray away from C#/Java world, I am amazed how bad the IDE experience is for other languages, but that's because most other languages have features which don't play well with IDEs (dynamic typing, templates, macros, anything compile time).
IntelliJ has much superior code completion even for dynamic languages such as Python and Clojure. I seem to recall having tested Javascript too, but I could be misremembering there as its been a while since I didn't use use Typescript.
I agree (even though it pains me to). I've thought about it a lot and I think it's because in the Java world, unlike most other worlds, the IDE is basically mandatory. I've worked in a few different java shops and the project was built around the IDE and required it.
I think you have it backwards. Java is actually very well designed in many ways, and that means that it's easy to make really good IDEs so they are popular.
In contrast it's really hard to make good C++ code intelligence features. For many many years Microsoft was the only one that had done it (as far as I know).
It's been a little while since I've worked with C++ professionally, but the project was cross platform so I'm not sure Windows and Visual Studio was ever a feasible option.
Most of us were using Xcode, but at some point I discovered CLion and it felt like a big step up. Having proper CMake integration instead of needing to regenerate Xcode projects really helped, plus I've often found Xcode to be quite unresponsive and never really liked the way it tries to be different with stuff like code navigation (recent versions seem to be better with how they handle tabs etc.)
But CLion is relatively recent. Quite possibly VS was the only IDE that did that stuff well for quite some time.
Not sure what time scale you had in mind with "many many years" but the commercial third-party extension Visual Assist has been the only serious option for robust and scalable C++ code navigation (and related features) in Visual Studio since the late 1990s, early 2000s until the present day. Visual Studio's built-in Intellisense has been trying to play catch up (and has somewhat closed the gap), not the other way around. There were also widely used products like Source Insight focusing on offline whole-program code analysis and navigation, but they weren't really designed for integrated development.
That said, your thesis about the relative difficulty of doing this for C++ vs Java seems hard to argue against, and the rapid, continuous growth in C++'s surface area and complexity since C++11 surely hasn't helped.
