WSL1 mostly had problems due to the layering violations and poor design decisions in the windows kernel and low level system libraries. E.g. filesystem functionality like "what constitutes an acceptable filename?" or "is that file locked?" is not only implemented by the NTFS driver and filesystem layer but also partly or fully by a number of higher-level system libraries. A lot of that lives on top of the windows syscall layer.
The Linux syscall layer (which is most of WSL1) lives next to, not above the windows syscall layer. But e.g. for all that filesystem access functionality, WSL1 doesn't just have to talk to the NTFS driver and generic FS layer but also to a lot of Win32 system libraries. If it doesn't, things will break. If it does, you have dependencies across layers, syscall conventions and system services. WSL1 didn't work because windows internals are a mess.
The Linux syscall layer (which is most of WSL1) lives next to, not above the windows syscall layer. But e.g. for all that filesystem access functionality, WSL1 doesn't just have to talk to the NTFS driver and generic FS layer but also to a lot of Win32 system libraries. If it doesn't, things will break. If it does, you have dependencies across layers, syscall conventions and system services. WSL1 didn't work because windows internals are a mess.