What the passenger wants is a cheap seat. And by cramming an many people into as tight a space as possible, allows the airline to give the passenger what he wants .... a cheap seat. No metric has ever been more important to a passenger choosing an airline, when paying for his own fare.
If any airline, was ever successful in charging more for more room in basic economy, then yes, I'd say there was hope for more room. But that will not change as long as passengers continue to choose .... a cheap seat.
Never gonna grow up, never gonna slow down .... Barefoot Blue Jean Night