The mainframe world is rather specialized which makes this an even harder challenge. First, there is a small group of non-IBM mainframes, such as Groupe Bull (formerly Honeywell). There may Unisys out there as well. Some companies must support more than one depending on prior data centers' legacy.
Within the IBM world there are specialities:
1) Computer operators: physically run the machines -- handle things like printers, tapes and cartridges, disk drives. Much work is automated now (disks are usually fixed, cartridges have auto loader silos), but there is stuff to be done. 2) System programmers: This is specialized people who maintain the operating system for a particular installation. There are three operating systems, MVS, VSE, and VM. Some companies must support more than one depending on prior data centers' legacy. 3) Application programmers: Usually COBOL and CICS, but there are various database programs new and old; plus other work in Fortran and Assembler. 4) New stuff like Linux and C and web development. Some centers use the solid COBOL/CICS on the back end and GUI on the front end to get the best of the old and new worlds.The mainframe world got overpopulated in 1999-2000 with many people trained and hired to work on Y2K conversions. Mainframe people were once in great demand, then the market collapsed (at least in NE US) and many people were laid off, never to work again in the field. Others took a 50% cut in pay just to have a job, such as a senior person earning $80k forced to take a junior position making $40k or else pump gas on the overnight shift.
The mainframe takes a lot of care and support. However, it has tremendous capacity to serve thousands of users simultaneously very reliably and very quickly. It is extremly rare that my employer's mainframe or its traditional network goes down. Remote networks, servers, and local PCs go down all the time. The hardware revolution in cheap memory has hit mainframes as well, and the boxes have tremendous memory and speed.
The mainframe's basic architecture is great at keeping the system from crashing from errant programs. The basic storage protection works great. The channel system for I/O is much better than a "bus". The operating system assigns peripherals to the proper application and prevents mixups.
One advantage of older people is that they've made every mistake they're gonna make and have years of experience behind them. If there is a problem, they'll know where to fix it fast.
The article mentioned people passing on. Sadly, that is true too, I just was at a funeral for a wonderful woman who died suddenly at 61 from a stroke. (She was a smoker, FWIW).