What people aren't realizing is that KCM Naruto doesn't consistently have V2 Raikage level speed. He blitzed Kisame in a "flash" like way, only to get himself stuck in the ground and sprain his ankle. He managed to react to the dodge V2 Raikage's speed (which is more of a reflex feat rather than movement speed feat) and that was the final time we actually saw that level of speed being demonstrated by him. It wasn't until BM did Naruto have that consistent flash-like speed and have full control over it.
KM Naruto without clones is undoubtedly going to have his hands full against a gated Gai, and while he might best Gai through a prolonged battle of attrition, the fight won't last long for the gate side affects to kick in when Kakashi is Kamui-sniping him from a distance. Naruto's ability to dodge Kamui whilst in KM mode is questionable to begin with, let alone while he is being occupied by an equally speedy and physically powerful fighter.
