If you are off the throttle for any length of time in a Rotax, it will take a bit to get going. It stands to reason that if a Rotax spools up at 7K, and takes all day to get there, it’s better if you can keep the rpms up. And, as Tony suggested, you could be overstuck (especially with a 32mm kart on D2s), which will bog you down even more.
Everything else Tony said was spot on. If you are new, your fellow racers will be happy to help (until you start beating them).