not at all qualified to give advice on music composition, since (other than the sukeban soundtrack) I haven't properly finished a song in about a decade—trying to make music solo is hard, y'all, always open to collabs—but I can apply stuff that I'd mostly say regardless of artistic medium to music

first: if you like an artist's work and want to do something similar, don't try to figure it out in a vacuum. go study their influences. given that their influences have influences this is of course potentially an endless rabbit hole, but 1. you don't want to just xerox their work and 2. having a better grasp on not just what is there but why it was put there makes it easier to not only use that specific technique, but also to think more deliberately about yr own choices. even if you're a more intuitive artist than an analytical one, you need a toolbox to work with.

second: the question on your mind when you're trying to analyze art should be "why am I being presented this, in this way?" a cool thing about music in particular is that it's really easy to put this into practice. if you're interested in how a song works, try to transcribe it. if you don't have the ear for that yet, try your best and then look up a chord chart or sheet music. maybe as transcription practice, try to correct their transcription, because it's probably very wrong. then play through the song. getting the sound into your fingers makes it much easier to notice when certain musical ideas recur across a discography or across a genre. is the song primarily on a different instrument than you play? are you a singer and it's an instrumental? even better. now you're learning arrangement, in a very practical sense. beyond transcription, especially if you can't play an instrument, try to break apart the song on a structural level. mark verse/chorus/bridge (or refrain/bridge in ballad form (pls look up ballad form)), noting where the same section sounds different, how the lyrics and music seem to reinforce each other or stand at odds.

third: cribbing from bill wurtz here. (google "fagen escape" bill wurtz to find reposts of his writing on this. 3 up borrowing in particular was like "oh holy shit that IS a common thing isn't it.") theory is really useful but it's worth figuring out some concepts on yr own and having a shorthand for them. I'm bad at applying this, the concepts that stick in my brain are either expressed in something approximating theory (ii-V-I of IV) or are just called, like, "THAT progression," but it's still helpful to me to realize that I don't have to drain myself trying to find a theoretical explanation if my goal is practical usage. helpful to at least know the popular name (e.g. royal road) but not. necessary.