True.
It also doesn't make sense for any jutsu to be an instant win in the Narutoverse. Every jutsu has it's pros and cons. Why would Amaterasu be the only exception? Hell, Naruto is destined to be more powerful than Sasuke (he's the main character), so how is Amaterasu an instant win if it can't beat Naruto?
Amaterasu has a start-up time where the user has to focus, in this time there are warnings such as the eye bleeding and a strong chakra pressure. This start-up and early warning will give opponents time to choose a course of action. Once Amaterasu is released, it appears as a fireball which is avoidable, as we've seen Sasuke and Ei avoid it and Gyuuki block it. If it strikes something it burns rather slowly, or at least not faster than any other Katon. Sasuke was able to survive long enough to use two jutsus, and burning his torso like that, if it burned too fast he would had become paralyzed from damage to his spine and eventually died from damage to his vital organs. Gyuuki also lasted long enough for Bee to escape (Bee's clone also didn't poof), Karin suffered only minor burns despite burning for a few minutes, and that fodder samurai was shielded long enough by his armor.
Amaterasu's most dangerous qualities seems that it can't be extinguished by ordinary means, burns things that normally cannot burn, and the user can control it's trajectory.
One of the things that I love so much about the series, anything could happen no matter how powerful a character is. A fight is based not on just raw power like DBZ but rather by match-ups, intel, strategy, terrain, circumstances, etc. So it irritates me when people try to rip the joy away from me.
A perfect example is Tsuchikage Muu vs. Mizukage Hozuki. One can fly, has amazing sensing, becomes almost completely undetectable, and shoots mini-nukes. The other has an Izanagi-like ability, cannot be sensed, has water logia abilities, and a killing joke. These two somehow fought to a draw.
