It's all a matter of trade-offs. So yes, whilst you can do a lot of stuff very easily in Python, it still doesn't make it the best choice for everything. It's also worth pointing out, that you can perform any possible computation you want in any programming language that is Turing complete, so anything you can do in Python, you can do in C, you can do in C++, you can do in Java, etc.
So, a bit more about the tradeoffs. Python has been designed to be a language that is incredibly easy to use, to learn, and is incredibly low-friction, but these benefits come with costs:
- Maintainability is a big one. Python is designed to be incredibly low friction, so you can very easily hack something together which does what you want extremely fast. The problem with this though, is the fact that friction that other languages provide, in lets say their type systems, make it much easier to write more maintainable code, even if it takes more time to write that code in the first place.
- Performance is the second big one. Python, again, in order to be low friction, manages a lot of things for the programmer (such as memory) that they otherwise would have to manage themselves. This makes writing programs incredibly easy, but comes at a performance cost.
- Multithreading. This is very Python-Specific, but the GIL (global interpreter lock) is a pain to work with I've heard.
- Libraries are also important. If you work in a particular field, if everyone in that field is using C++, then all the tools you are going to want to use are going to be written in C++ as well, and the libraries that help you do things in that field won't be as mature in other languages such as Python. This means that even in cases where you might prefer one language over another, the tools available may just nudge you in the other direction.
I hope my post makes sense, discussing the tradeoffs between different languages is a huge field in and of itself, but I hope this gets across the idea that there isn't "one ideal language", and that programming languages are just tools, and different tools are better for different jobs.