I would have liked to see a little more connection between this ending, and what we know of our heroes based on Robert Louis Stevenson's Treasure Island - of which Black Sails was explicitly presented as a prequel.
Black Sails ends with not even a hint of Flint becoming a pirate again. I have no problem with his giving it up for the man he loves, but I wanted to see at least a hint, a suggestion, of how he got back on the high seas again.
Otherwise, the ending was strong. Long John being turned away by his love is a good entree to his subsequent life with the skull and crossbones. Billy Bones surviving was necessary, as he, too, is spoken of by Stevenson.
Rackham was a real person in our history, and he did not have a happy ending. There was no indication of that in the Black Sails finale, other than a life of piracy cannot have a happy ending, but that was ok.
But back to Flint. Long John's strategy of giving Flint what he most wanted, so he would give up his quest to change the world didn't work as an ending even if we didn't know what Stevenson had in store for him. Finding Thomas could well have invigorated Flint, made him even stronger in his resolve, to right what he saw as wrongs in the world.
Still, if the finale was not as good as it could have been, the overall series was memorable and I'd highly recommend it. May piracy on the seas live forever as a form of fiction in print and on the screen.
See also: Black Sails 4.1: "True Friends and Mortal Enemies" ... Black Sails 4.2: Bones vs. Flint ... Black Sails 4.3: Decisive Victories and Losses - On Both Sides ... Black Sails 4.4: Chess Game ... Black Sails 4.5: Bold Moves ...Black Sails 4.6: Spanish Horsemen with Lances ... Black Sails 4.7: Jack Rackham and Fake News ... Black Sails 4.9: Flynt vs. Long John ... Black Sails: Penultimate
See also Black Sails 3.1: Restored ... Black Sails 3.2: Flint vs. Sea ... Black Sails 3.3: Gone Fishin' ... Black Sails 3.4: Mr. Scott's People ... Black Sails 3.5: Alliance ... Black Sails 3.6: The Duel ... Black Sails 3.7: The Blackening of John Silver ... Black Sails 3.8: Whether Vane? ... Black Sails 3.10: Wither Vane ... Black Sails Season 3 Finale: Throckmorton
And see also Black Sails 2.1: Good Combo, Back Story, New Blood ... Black Sails 2.2: A Fine Lesson in Captaining ... Black Sails 2.3: "I Angered Charles Vane" ... Black Sails 2.4: "Fire!" ... Black Sails 2.5: Twist! ... Black Sails 2.6: Weighty Alternatives, and the Medium is the Message on the High Seas ...Black Sails 2.7: The Governor's Daughter and the Gold ... Black Sails 2.9: The Unlikely Hero ... Black Sails Season 2 Finale: Satisfying Literate and Vulgar
And see also Black Sails: Literate and Raunchy Piracy ... Black Sails 1.3: John Milton and Marcus Aurelius ... Black Sails 1.4: The Masts of Wall Street ...Black Sails 1.6: Rising Up ... Black Sails 1.7: Fictions and History ... Black Sails 1.8: Money