No, I'm not.
Minato against Kakashi has 2 basic options to use FTG:
a) He can try to mark Kakashi himself, which would pretty much result in Minato's win. This is, however, dangerous for him, because he needs to get close to Kakashi. While Minato's speed is much higher than Kakashi, it's not enough to stay out of his sight. Thus, Kakashi has chances to Kamui him in that moment.
b) He can hide himself from Kakashi and throw marked kunais at him. After a kunai gets close to Kakashi, he can teleport to it and then use Rasengan. While this technique is less risky to Minato, there is a risk of Kakashi noticing the Kunai and kamuing or stopping it otherwise.
Additionally, both of these methods have another counter - Kage Bunshin. If Minato by mistake performs any of the two strategies and kills only a clone, he's probably done for, because real Kakashi would watch from hiding and kamui Minato as soon as he shows up.
The more massive the object, the more time it takes to warp it. If every Kamui required time, then Obito would have noticed Kakashi kamuing Naruto in front of him (especially with a Sharingan). Against Minato, no huge Kamui is needed.