> not really being compatible with modern hardware

Yes. That's correct. You are correct. It is no longer fit for purpose and hasn't been for a long time. But inertia.

> the only way to fix it requires breaking all clients

Do it.

Rip the OpenVMS, SVR4, and HP/UX roots out of the ground and throw them in the trash, next to telnet and SysV filesystem support in the kernel.