VM is about as "Old school as it gets".
Remember the IBM 360, PDP-11s? Everybody tied into it. Nothing was local.
I prefer to keep my stuff local so in the event of a Black Swan event, I still
have data I need to make survival easier. Memory is cheap today.
Use it or lose it.
I'm not sure about your environment, but we simply accessed the IBM mainframes using terminals due to the classified nature of the job.
Nobody had PCs until the mid 80s at my unit. Even then, PCs were for the secretaries plus one in each office setup on a separate desk for all to use.
Most of those mainframe or mini-computer environments involved running X11 clients (PCs, DEC workstations, etc.) with the servers running the apps and displaying the interface on the client. Totally different from a VM.
We had an IBM 4331 running VM software, but all the processes were contained on that machine with access provided by 3 terminals connected to the host and 2 VMs. The machine emulated an IBM 360/370 with unlimited virtual devices.
I'm not sure what timeframe you were referring to, but being able to run a virtual machine with a full-blown O/S isn't something I'd call old school relative to dual boot.