The write cycles shrink faster than the capacity grows.
The same applies to storing multiple bits within a single cell via multiple voltage levels.
MLC, TLC and QLC all require more accurate voltage measurements which become less and less reliable as the voltage drops with each write.
The only remaining way to increase capacity without downsides is by adding more layers.
After that there is no option other than switching away from NAND.
Smaller lithography processes impact write cycles negatively.
The write cycles shrink faster than the capacity grows.
The same applies to storing multiple bits within a single cell via multiple voltage levels. MLC, TLC and QLC all require more accurate voltage measurements which become less and less reliable as the voltage drops with each write.
The only remaining way to increase capacity without downsides is by adding more layers.
After that there is no option other than switching away from NAND.