I am of the opinion that Holdo and Leia were absolutely correct to not trust Poe with any of the plan, given that he had literally just demonstrated himself to be an insubordinate, short-sighted glory hound who was willing to throw away irreplaceable lives and equipment for a pointless "big ship kill" against a freaking bombardment monitor which was zero further threat after they'd abandoned their base.. He basically lived down to literally being named "Damn Moron".
I. Dunnow, witholding the plan from anyone aboard the rebel ships seems silly when the alternative in peoples minds is 'we're running until out of fuel, and then we shall die'. That kind of prospect would encourage damn-fool behavior.
But, that aside, the dreadnought getting blown isn't shown to be as negative as it maybe should be? When they get into that chase sequence, Poe being wrong gets argued against because now at least the new-Imps don't have the big-ass laser cannons with them that would presumably be quite a problem for the shields.
Poe also kinda has a point? New-imps just blew away Republic resistance itself and, judging by intro credits, were stomping out on a conquest-spree. And in that context, getting a big ship kill--particularly a ship shown to be unique in such a way--is a important moral victory that can be held up as 'We didn't just run away!' To keep resistance active and hopeful.
That bit just doesn't make sense to me from a pragmatic level, and it seems to be quite different from TFAs Poe Dameron.
Could've been established better if, after destroying the first dreadnought, two or three more had vome out of hyperspace.
And if the entire Holdo and ship-scenes had been a bit more carefully plotted or explained (I forget now, was 'There's a spy' a concern ever brought up by Holdo or others, or is that purely a fan idea? Because if not, something to that effect seems needed to explain the decision not to tell people the plan where they don't ineviteably end up dead)