It's basically just much worse than 3 in every possible way. Luigi's moveset in particular was massively expanded and refined from what it was here in 3, and the environments became immensely more detailed and full of interactions after the second game was in hindsight so severely hindered by the 3DS hardware (which makes this port very weird to me). The worst thing about it is the mission structure, which makes exploring a slog since they arbitrarily change each accessible room ever so slightly in each mission, so you end up going over the entire level again and again checking the same spots for treasure. Even if you don't care for that and just want to beeline it, it's got an annoying stop and start structure with a lot of backtracking and busywork to stretch each level out over all these different missions. Collect the stolen gears to open a door or whatever, that sort of video game padding. It was also criticized for losing a lot of personality by dropping all the unique ghosts, which is especially felt in the boss fights which now pit you against such foes as "giant spider", "a bunch of regular ghosts", and "staircase" (I promise, the reality of that one is somehow much less cool than whatever you're imagining).
The first game is completely different from the others in its focus. It has the simplest gameplay, so the combat is mostly based on puzzles instead, with figuring out how to expose each ghost's heart so you can stun them and suck them up being the meat of the game (this aspect is not really a thing in the sequels). It's also got a notably darker and more grounded atmosphere that's more Haunted Mansion or "family friendly Resident Evil parody" than the outright cartoon hijinks of the sequels. It takes place in one contiguous mansion that has a lot more context to its rooms due to giving them bespoke inhabitants, and isn't divided into themed environments, with more expectation of traveling between newer and older areas to progress.
The addition of some Scooby-Doo shenanigans with flipping haunted house walls and slapstick comedy can't really make up for 2 gutting the atmosphere and characters that made Luigi's Mansion memorable in the first place. 3 managed to refine its new direction and make it work, in fact it's easily the best of the lot, but the first game is still very unique and has its fans for a reason. It just leaves 2 in an odd place, because it was so thoroughly outclassed by 3, and was pretty bland and forgettable to begin with. It's a very similar situation to Samus Returns and Dread, where a mediocre 3DS revival of a beloved Nintendo series outsourced to a western developer got an unexpectedly great Switch sequel that addressed pretty much every major problem with the previous game and left it completely in the dust. When I revisited 2 after loving 3, the only solitary positive I came away with was preferring the mechanics of 2's vertical plant area to 3's vertical plant area.
I would love the whole trilogy on one technical level (and with Ray-Tracing on Switch 2 
)
