Yeah, that's pretty bad. The fact that mounting the volume as a network share gets better performance is surprising and somewhat concerning.
However, what I was talking about performance-wise was the overhead of every system call. That overhead is gone under WSL2. Maybe it wasn't worth it for that reason alone, but original WSL could never keep up with Linux kernel and ecosystem development.
Being able to run nearly all Linux programs with only some operations being slow is probably still better than being able to run only some Linux programs with all operations being slow.
The problem with WSL1 was the very different file system semantics between Windows and Linux. On Linux files are dumb and cheap. On Windows files are smarter and more expensive. Mapping Linux file system calls on Windows worked fine but you couldn't avoid paying for that difference when it came up.
You can't resolve that issue while mapping everything to Windows system calls. If you're not going to map to Windows system calls then you might as well virtualize the whole thing.
However, what I was talking about performance-wise was the overhead of every system call. That overhead is gone under WSL2. Maybe it wasn't worth it for that reason alone, but original WSL could never keep up with Linux kernel and ecosystem development.
Being able to run nearly all Linux programs with only some operations being slow is probably still better than being able to run only some Linux programs with all operations being slow.