Was he completely incompetent except for being cautious to an autistic degree and having a strong stand...

He was very competent at running the gang for 15 years. The only reason why he lost is because it's a story for kids and the good guys always have to win even when it makes no sense.

>What exactly does he do to warrant being a ''honourable gangster'' beside not liking drugs being sold to kids and trying to protect Trish from the Boss
Aside from literally the entire town loving him for helping everyone that comes to him? Nothing you say makes sense. He is literally a criminal that is a good person, him being a criminal doesn't contradict him being a good person and being a good person doesn't contradict that he is a criminal. He tries to do good in his realm and situation, that's all it is.
>But the goal is the same. And that never went anywhere anyway
That's speaking from the perspective of the viewer. For the characters it's perfectly logical to act like they do. What is and what isn't pointless from a story telling perspective doesn't matter to the motivations of the characters. You arguments are all over the place focusing on characters, story, premise, writing even when talking about a single aspect of the entire story.
>Bruno to retaliate immediately, that does not suddenly make him a ''honourable gangster'', the character has no choice but to attack
No, by all means he doesn't need to attack because he figured out it was the boss. He was willing to take the consequences of attacking the boss to safe trish, if that is not honorable to you then I don't know what is. And again, it's irrelevant how the story went, how irrational and fucked Diavolo acted or how bad the writing is. Nothing contradicts Bucciarati being a honorable gangster.