Historically one of the big problems with Xcode has been that they only dogfood. There’s people on the team that have not touched any other IDE in decades. They’ve gotten used to all of the quirks, and just don’t really know that things could be better. Every new improvement has to be designed from scratch rather than just ripping off what other IDEs do better.

Apple internally has structured their projects to not run into all of the debugger performance cliffs, but don’t provide any guidance on how to do the same thing and don’t proactively fix the problems they’ve avoided.

Every time I’ve talked to someone who has worked on Xcode they’ve expressed the opinion that Xcode is best-in-class and they simply don’t understand why people disagree.