Your proposition focuses on something impossible, attempting to counter story plot points with the presumption of reality. The question of whether Finn would have succeeded is moot because STAR WARS is not real, and because it's not real there's no way to tell what would happen outside of the story. (Moot meaning arguable, not pointless, and as people can see the argument never ends until understanding is brooked.) My understanding of your statement, therefore, isn't about the reality of the story points -- but rather the depiction of story narrative. As depicted, the story points did not satisfy you -- and you use words like "internally inconsistent" and "[in]competent" to express your disappointment with said depiction. Yes, I well understand that TLJ gave you some things you didn't want to see. The difficult part for you is that other people have a different opinion, which is why using phrases like "cognitive dissonance" is often bushleague trollwork and self-incriminating.
To ignore analysis that understands and appreciates the film, and say stuff like "Even if Rian Johnson flat-out says otherwise I don't care" -- that's cognitive dissonance.
But I wouldn't say it's pathetic per se.
This is oversimplification and that's not your fault, namely because this is a STAR WARS film. No one expects nuance from a pew pew lasersword.
The film isn't about sacrificing oneself for the greater good as it is about Doing Right Action (lol, I used Purity of Intent at one point; I can only imagine the eye-rolling here), that is: accounting for the cost involved in taking such actions. As examples: Poe was right in wanting to destroy the Dreadnaught, AND Leia wanted him to learn the meaning of casualties. Finn was right to want to defend Crait BUT he shouldn't die because destroying the cannon would not have been much defense due to the remaining First Order fleet and the lack of Resistance aid (remember: Rose has no idea Luke will arrive). Holdo's command has no obligation to inform Poe BUT her actions led to rash planning and mutiny.
It's easy to not-appreciate this level of mature decision-making when you want things to be simple and obviously one way or the other. Ambiguity and ambivalence are not always welcome, particularly in films that started as kids' films.
