Just a disclaimer, I haven't watched the movie before DMTNT, but thoroughly enjoyed the first three of the series. What I noticed right away was how Jack did almost nothing in the most recent movie. He was literally just a character the movie used to garner laughs from the audience whilst acting irrationally stupid.
Contrast this with CotBP's Jack Sparrow, and they couldn't be more different. His ability to trick people with words, eloquently fight with Will Turner in the blacksmith's shop, actually present himself as "one of the worst pirates" who's actually known... What the hell happened here? It's like the executives just looked at the superficial qualities of Jack in these first few movies and thought, "We'll need Jack, but just all the funny parts!" That resulted in one of the most hollow, one-dimensional characters I've witnessed.
Not to mention CGI quality... What I find amusing is how select movies from early 2000's have such good quality that stand to this day. Why? Because they're able to utilize CGI as a tool, rather than a fall-on cover. Sure the skeletons in CotBP could use a bit of a workup, but aside from them, I thought the movie held very well for being almost 15 years old. You look at DMTNT, and it's just littered with (IMO) unneeded CGI, resulting in almost a comical movie that takes you out of the experience and thinking, "Am I just watching someone's experiments with how far s/he can push with CGI?"
And lastly... Plot! What happened to a good plot? CotBP was simple - Pirates come to take Turner's "daughter," tried to break their curses, and then you insert the amazing fighting sequences. DMTNT, while its plot skeleton was simple, seemed like a kid who came up with all of his "great" ideas in the last minute. I felt like I was watching an episode of Scooby Doo when Turner came up with the last minute idea of breaking the trident. Or when Carina figured out that all but one star were lit up on the island? Or when Barbossa revealed to his daughter just minutes before his death?
In theory, this movie should've been much better. You get a backstory of Jack Sparrow and how clever of a pirate he was to take down a fleet led by Salazar. You get a theme of son saving the father, similar as to how Will and his Father in the earlier movies. You actually get to see Will and Elizabeth! We're presented with the formidable Captain Salazar and his crew. And of course, we got to see Captain Barbossa with the Black Pearl. It's just that disappointing, then, with how flat these directors executed the movie.