I like KH3's soundtrack. Based on my experience playing the game, I'd say they focused more on the
feeling the song gives the player, rather than just making the melody something memorable. Whether this is a good move is totally subjective, but I found it pretty effective throughout the Disney worlds. The songs made me feel the same energy as the movies the worlds were based on. Ultimately, though, I was disappointed when there were so few new pieces for the KH original characters/worlds/etc.
A general gripe I have with KH3's soundtrack in general, and part of why I think the new tracks aren't as memorable, is the blending of the orchestra. I haven't given any new pieces other than the theme songs and Scala an isolated listen, but I remember playing the game and being irritated at how hard it is to pick out one specific main melody. I've been playing in band and orchestra for 10 years now, and directors LOVE to tell us to blend our sound. It's very evident that that was the direction taken for the recording of the KH3 soundtrack, because while the sound of each track is cohesive, it sounds like it's a homogeneous block, rather than a layered and complex track. This may have been the goal of previous games' scores, but it didn't really show because of limited soundfonts/soundchips if I'm not mistaken. I believe KH3 is the first full KH game to have an orchestral score, so it's the first one to have this kind of sound quality/"problem." (I hesitate to not put quotes around that, in case someone DOES prefer a blended sound.) I think 0.2 might have had an orchestral score too, but I don't remember the sound being too homogeneous. It might have to do with the fact that most of the tracks were rearrangements of previous tracks, which are already iconic, and thus the balance can't be fiddled with too much at risk of making them sound
too different; that's definitely the feeling I get from the orchestral soundtracks for 1.5 and 2.5, which have a more blended sound than the original PS2/PSP releases, but still have audible layers, some of which even make previously buried parts shine! Special mention to the guitar in Lazy Afternoons here, I love you, thank you 2.5 for letting me finally hear it clearly
Basically, though, this is a very, VERY niche complaint. It's just been on my mind ever since KHO World of Tres' sad excuse for L'Impeto Oscuro, where the first violin was not playing NEARLY loud enough during the violin-cello counterpoint duet. Y'know, the sexy violin part where the violin is supposed to shine? Instead of going ham, the way any musician should when playing Yoko Shimomura's music, the first violin's sound just... blended in with the rest of the orchestra. I was already not expecting much from the cello, given its low register, but I was seriously disappointed by the
first. Violin. Basically the star of the orchestra... and you don't stand out during your solo???? Yeesh. Young Xehanort himself would never.
TL;DR KH3's soundtrack is better at making you feel than being an earworm, but a lot of its non-memorableness comes from an overly blended orchestra which masks any parts that would otherwise stand out.