I think you're half right.

On one hand, I don't see many of the modern services having years to decades of uptime. Clustering is also bolted onto many products while not available for most products. These were normal for OpenVMS deployments. Seems like a safer bet in that regard.

If people have $$$, which VMS requires for such goals, they can hire the type of sysadmins and programmers who can do the same in Nix' systems. The number of components matching VMS's prior advantages increases annually. Also, these are often open source with corresponding advantages for maintenance and extensions.

The other thing I notice is VMS systems appear to be used in constrained ways compared to how cloud companies use Linux. It might be more reliable because users stay on the happy path. Linux apps keep taking risks to innovate. FreeBSD is a nice compromise for people wanting more stability or reliability with commodity hardware.

Then, you have operating systems whose designs far exceed VMS in architectural reliability. INTEGRITY RTOS, QNX, and LynxOS-178B come to mind. People willing to do custom, proprietary systems are safer building on those.