Python is getting faster but is still far from what you can get with C++ of course. That said, for simulations you likely don't want everything in Python or in C++. Part of the challenge is to split the subsystems properly and use C++ where it matters.

Like it or not, this is definitely filling a very unique niche. It's a very good fit for system software where safety is important and available time limited. There is no better option for now.