Yes but no
(There are some interesting comments on HN and rebuttals by Liam. But here is my take.)
usually completely ignoring all the lessons learned in the previous generation
Umm, not really. RSX-11 on the PDP-11 was a decidedly calculated subset of OS/360 on the competition's machine. It had file IO added (and the whole almost-flat filesystem) but the rest is fairly simple process management etc. IBM's designs were good enough to copy. And added to the 16-bit cheap-ish CPU that was a follow-on to numerous other designs by a very experienced software and hardware design crew at DEC.
The notion that lessons were not learned I think is incorrect. The lessons were very much learned: Choose the best two-thirds of your competition's product, add your own third. Sell and sell hard. (And, as always, beating IBM on price is child's play.)
The Symbolics stuff was legendary (at the time) for complexity and cost. And uselessness -- were there any actual software products sold requiring a Symbolics machine? Nobody buys $100k machines to heat up a room with the wasted power. You have an expensive user because they have skills (orbital calculations, microprocessor design, chemical plant optimization) so you buy them an expensive tool. Who bought a Symbolics workstation for an end-user? Anybody? Bueller?
Another example: the IBM 360 series had the optional model 2250 display. It was early days and used a light-pen to detect the flash on the CRT but it sold well because there was design software to go with it. That was the beginning of the workstation era -- build or design things quicker with interactive computing. Only affordable by mega-corps but the market was then "proven". And competition quickly appeared.
I don't claim the notion that a skilled thinker could manage to produce useful products with LISP-like languages is wrong. Arguably the equivalent modern example is the construction of WhatsApp by a handful of people using Erlang. Now that is an exotic language.
These are cases where the product filled needs of the market. Sometimes the market didn't even know it needed them.
Arguing over New Jersey/Stanford or MIT "approaches" is irrelevant. Designers do what designers do and adding post-facto explanations by technology historians is not adding anything useful.
There were only these two schools of thought you say? Oh.