CPUs and their ISAs evolve continuously, as a function of their intended areas of application and of the available and anticipated semiconductor and packaging technologies. The primary driver is ROI (return on investment). The Burroughs architectures were developed at a time when restricted memory size and small gate count were major limiting factors. Those architectures are not really appropriate for today’s CMOS technology with microscopic gate sizes, where heat dissipation and unwanted quantum tunneling are major issues.
The recent side-channel attacks on speculative-execution CPU features do suggest that barrel processors, which is an implementation technique that has always been appropriate for hard real-time applications such as avionics engine control, might become more generally relevant, particularly in conjunction with lightweight threads such as Rust offers.