In my experience many junior developers love mode switches, because they aren't sufficiently scared of complexity. "Yeah, lets add a setting to turn on or off advanced mode. Then the power users and the noobs will all be happy!".
After some time in the trenches it becomes clear to most that mode switches lead to combinatorial complexity and should be avoided at all costs.
Today we call them “feature flags”. Definitely an anti-pattern.
That said, I was once at a customer's site that had an original "blue and white" MV/8000 (the MV series in general were brown-clad). If I remember correctly what the admin said, they boot up the new 32-bit OS, AOS/VS, for part of the day, and an older 16-bit OS, either RDOS or AOS, for the rest. I wish I remembered this more clearly.
And of course the VAX-style instruction set that West's architect envied fell out of style, didn't it?
I dotted lined into Tom West for a time at Data General and, later, had a >decade stint at Red Hat where I got hired on by a senior ex-DEC person.
I for one look up to people who can design, implement and debug complex systems, especially computers components and low level computer software.