Its like, python can be 400 times slower than C++, but people still use it.
Yeah, because people use python when it doesn't matter and c++ when it does (including implicitly by calling modules that are backed by c implementations).
That is not an option with FHE. You have to go all in.
For compute, which is a small part of things computers do. Many things are I/O and network bound.
I’m not at all a fan of Python, but perf is the least of my concerns with it.
If Python devs/users had to actually use all pure Python libraries, no C bindings or Rust bindings, no RPC to binaries written in faster languages, it would get dropped for a ton of use cases, absolutely including its most prominent ones (machine learning, bioinformatics, numeric analysis, etc.).