Context switches between processes are bad, but going into the kernel for an irq using things like aio and io_uring which can populate events into a result ring

Context switches between processes are bad, but going into the kernel for an irq using things like aio and io_uring which can populate events into a result ring buffer doesn't add a ridiculous amount of overhead. Optane DIMMs avoided that, but the consequences were such that the hardware had a lot more complexity. Doing something like an FTL at DDR4 speeds and latency is very difficult. Plus you don't really want to expose hardware that requires wear leveling directly to applications, as a buggy app can wear out (damage) the hardware prematurely.