I've never seen Arcane, but I'm sorta the opposite in terms of paying attention to major/minor characters.
I was never a huge fan of the hero archetype. I always liked the friend/sidekick of the hero who gave them advice, or aided them when they were down or in trouble. Guess I'm all about brains, not strength.
Characters like Gandalf, Master Shifu/Oogway from Kung Fu Panda, Yoda, Miyagi, list goes on.
Then again, maybe Mentors are moreso main than minor, I am not sure anymore.
I guess what I'm trying to say is that I remember both major and minor, but those considered minor seem, to me, to make the most impact, or at least tie everything together and keep the hero being the hero.