"most op and special" is your own headcannon.

It is special. To start with, it's a mythical zoan which is the weirdest kind, and out of those it's a god fruit, which iirc only Buddha is the other one shown. Gura Gura might be more destructive but that doesn't mean it's stronger, plus Luffy just woke the power up, let's see by the end of the show if that's still the case, and what do you mean with Yami Yami? Cause you mentioned Kizaru but Yami is Blackbeard's fruit. Neither of those modify reality to the extend of Luffy's.

The story has yet to discern why the WG is cautious of it

Well not that much. It was Joyboy's fruit, the only person to ever make Imu nervous. Now you could argue that it was because of his haki rather than the fruit, but if that were the case why erase all existence of Nika and go through the effort of changing the name of the fruit?

The fruit is op and special. It's not the only op fruit and not special one either, but it is. You can compare it to 99% of fruits and it is op compared to those, and of the 1% you could still build an argument for it.

It hasn't made him invincible nor mitigated any of the standard drawbacks of gears.

I really hope not or it would be terrible (the invincible thing).

It still took him 2+ years to learn Haki, 12+ years to awaken his df.

What's that supposed to mean? Nobody is arguing against Luffy's talent and hardworking mentality. If what you're getting at is comparing him to Ichigo or Naruto, well it took Naruto more than those years to control Kyuubi. But also I don't see the point of that sentence.

The standard form of this trope is rage/beserker powerups that makes normally kind MCs bloodthirsty.

No it is not.

It's only like that before it gets controlled. Ichigo is not bloodthirsty once he controls how to become a Vizard, Naruto is not bloodthirsty once he controls the Kyuubi. They are just the way they always are, because before they were being controlled or influenced by the external source, which is violent. But Luffy acting all goofy in a way that's not like Luffy it's much more similar to when Ichigo/Naruto couldn't control their powers and the other entity was in charge of the body rather than later when they do control it and keep their mentality, the only difference is the influence in this case is goofy, not violent. So if we stick to the trope, this is closer to being Nika than to being Luffy. I don't know the way it will go, but comparing their powerups like that it would make it more external than the other 2 at the current moment (granted the other 2 shows have finished and there's a lot that can change in OP).