This is of course far from true; CTSS and especially ITS (which was so programmer friendly that rather than what is called today a “shell”, it’s user interface was a debugger) long predated it and both Thompson and Ritchie were exposed to them while at MIT to work on Multics. The supreme programming environments for programmers, the MIT Lispms and the D-machines at PARC are the ultimate in programmer-friendly OSes that are, for various important reasons, unmatched today.
Also, in their early papers about Unix they talked about how they didn’t need all that fancy stuff that mainframe systems like Multics needed, like VM and IO modules (Unix just does everything through the kernel in a simple fashion). Well, it was for a small computer system. There were good reasons that mainframes were structured the way they were and by the mid 80s that model started migrating to workstations (e.g. Britton-Lee accelerator and graphics subsystems) and by the 90s that model was already quite common in microcomputers too (for example with mpus in disk controllers and network interfaces).
But the Unix cultists ignored that revolution. They came late to the party with regards to networking; even when developing the sockets interface they relied heavily on the PDP-10 approach, but seemingly didn’t learn anything else from that.
Glad they are finally noticing that the world has changed.
Had it been a commercial product from the get go, and history would have gone quite differently.