How to upgrade skillset in mass?

I have worked as a VMS administrator for approximately 18 years.

VMS is a solid operating system, but it has grown out of favour with companies due to a number of factors that I won’t go into here.

Where that puts me is in a situation where all my operating systems, networking, database, applications, security, storage, etc. etc. are in areas that are increasingly out of favor, so I’m looking at trying to add additional skills en mass to my skillset if for some reason I find my self ever looking for work. I don’t see any particular skill being more important than the others, except for leadership which is the most important skill to have. Any thoughts?