About the Dreadnought destruction:
In the moment it isn’t heroic. There’s a shot of Poe looking at Paige’s bomber falling into a fiery inferno and he does a sad face.
And then while everyone’s celebrating on the cruiser, Leia looks at the death toll and sighs.
The movie’s take on self sacrifice is: Useless self-sacrifice is bad. Paige didn’t need to die. If the battle had gone differently, she would have lived.
Her sacrifice is only useless until it is revealed that hyperspace tracking is a thing, making their destruction of the fleet-killer retroactively heroic and vinticating Poe’s actions. Kinda muddles the message there.
Holdo needed to destroy the Supremacy and only had one way to do it.
Actually she needed to destroy all of the Star Destroyers and had a one-in-a-million chance of doing it. It’s a good thing she lucked out, because if even a single Destroyer was left operational, hindsight would have made her death a ‘useless self sacrifice’. Kidna muddles the message there.
Finn’s self sacrifice wasn’t needed because it wouldn’t have changed anything.
I mean, it might have. He had better odds than Holdo, anyway. Kinda muddles the message there.
So in the first instance heroic sacrifice is bad (wasting life and equipment on bad odds), even when it is later revealed that this sacrifice saved everyone.
In the second, heroic sacrifice is good, even when it wastes life and equipment on even worse odds.
In the third, heroic sacrifice is again bad, and I don’t even need to know the odds because they are surely better than rolling a thousand natural 20’s on a total enemy kill.
The theme of TLJ is that noble sacrifice is bad when it isn’t worth the cost. Great. It’s just too bad that the text of the film contradicts and muddles that message at every turn.