I would absolutely love to have access to "dumb" flash from my application logic. I've got append only systems where I could be writing to disk many times faster if the controller weren't trying to be clever in anticipation of block updates.
And it breaks down the instant you change the hardware, even in the slightest ways. Frequently the optimizations then made turn around and reduce the speed below naive methods. Modern flash+controllers are massively more complex than the old NOR flash of two decades ago. Which is why they get multiple CPUs managing them.
It does need support from the storage device though.