It’s probably due to everyone already having been through Lost Mine once before that made it boring the second go through.
I'm the only person at the table who's done it twice, and I did it on opposite sides of the screen both times. Everyone else had a single go-around. This is purely from the standpoint of people who played through it once, and thus far are enjoying our romp through the area with a fresh set of eyes and an entirely new set of objectives and stories to tell.
I’ve both run and played both boxes too, and we’re going to have to agree to disagree here, friend. I found that DoIP has a very loose, bland plot made of a series of boring mini-dungeons. The Essentials Kit seems like it’s meant as a stand-alone product (though others here have indicated it was produced to sell along the Starter Set) but I was frustrated about how little it offered relating to the town of Phandalin or it’s people. The expansion content seemed pretty flimsy too. At least in the Lost Mine we met villains with some backstory and motivation.
I think the more minimalistic Phandalin is to its benefit; In Lost Mine, all the extra buildings and NPCs they had for you to meet were partly designed to be faction shills for the Adventurer's League factions, and their side quests were so numerous that collecting them all, doing them all, and then eventually turning them all in was such a chore. DoIP reconciled this by not detailing as many NPCs and directing the characters to a Job Board where any number of their current feasible tasks could be found, though obviously there's no pressure to do much of anything in a particular order (and in fact my players, without realizing, plotted a route around the area that took them far and away and brought them to places both earlier and later than intended).
I like Phandalin as a jumping off point, it's not meant to be this place where your characters are to earn a grand attachment to every Tom, Dick, and Larry, it's the first steps on a greater adventure. Which might explain why I like DoIP better, since the follow-ups rightly send you off to a place that needs you more urgently, and actually lets you stake a claim in the rebuilding of a waylain settlement while convening with the burgeoning town council. Phandalin is hailed as a place that has remarkably survived a lot of punishment over the years, unlike its contemporaries to the east and southwest respectively. I think the quality of it being settled and always eager for help, but never in dire straits, is a huge boon to its character.
