I think "no role" is an overstatement, though I get and agree with the main point that fatigue can be much less relevant than it should be.
One can get around subbing players through a combination of: using time outs specifically for replenishing Energy in the most judicious way possible, and players getting hot compensating for fatigue.
Another thing is that decrease in Energy has a lot to do with certain actions a player might perform during play, not necessarily time spent on the court. If you basically force offense to funnel through one guy dominating the ball, you'll notice that, while he loses a lot of energy quickly, the rest of the team stays extremely fresh, comparatively.