Some anecdata, three times in my career, I have worked on massive 1M+ line of code Java projects -- single repo. The initial Apache Maven download of dependent JARs plus indexing might take one hour or so. After that: Lightspeed. Yes, I do agree: When you are forced to invalidate your indexes, the next restart is painful.

More anecdata: One of my current projects is Python 3+. The indexing is much slower and less accurate. Plus, we use lots of binary libraries (compiled native code), which seems to trigger indexing on each restart. But whatever, get a 5GHz machine, give IntelliJ 16GB of RAM and let it run. In 2022, are there any serious alternatives besides a Titanic-sized IDE for enormous complex codebases? I don't see any that average developers (myself) will use.

Last point to mix big IDEs with C++: Visual Studio (as much as a cringe writing anything positive about Microsoft) is a phenom platform. For years, it absolutely dominated C++ IDEs. IntelliSense was mind-blowing in C++ and force multiplier that was unmatched for many, many years. It is still very impressive to me. I am sure they feel JetBrains' CLion biting at their heels!