If memory speed is 100ns then you would notice the memory bottleneck around the time when your processor speed is 10Mhz. This point was reached in the mid 1980s with the 286 processor. Yet through the addition of cache memory this bottleneck was hidden from most software. They continued to operate in a bubble as if they were still running on the hardware of the 1980s.
It’s a bit like life itself...we land mammals carry around bags of water under our skin and our cells are still batched in fluids as if we are still living in the environment of the oceans hundreds of millions of years ago.
Many programming languages have been invented since the 90s but as far as I know none of them explicitly model memory latency and make reference to memory hierarchies. It’s as if they still need to maintain the illusion that they are running on the hardware of the past.
(Note: I once read about a language called Sequioa developed at Stanford that explicitly modelled the memory hierarchy. I don’t know what happened to it).