It's hard to explode out of submissions with the gi so you rarely practice your explosiveness so that's why pure jiu jitsu players have way less explosive power than wrestlers. Explosiveness is crucial for mma.
ALOT of submission defenses with the gi require you to hold on to a part of your gi for defense. Like if someone sits back for an ankle lock, you're supposed to sit up and grab his collar for defense. And when someone goes for a kimura on you, you're supposed to grab your pants for defense. Or when someone has you in spider web going for an arm bar, you're supposed to grab your own collar for defense. Or when someone is trying to RNC you, you're supposed to grab both your collars.
How does the gi help your nogi defense again??
Remember, the only guy to escape Marcelo's RNC in ADCC was Diego Sanchez who had never trained in the gi at that point. His explosiveness got him out