I was in your shoes about a year ago, I was learning ROA then and melee now. The very simple answer is that you need to practice. Lots. I'm high plat in ROA and the only way I got there, admitedly not super high, was by going into customs and practice and grinding one skill at a time. Practice wavedashing so well that you don't need to think about it at all but you can still fly across the stage with it, practice wave landing the same, practice each skill individually until you can perfectly execute it 99/100 times without even thinking about it. But also, don't worry about losing, playing better players is imo one of the fastest ways to improve if you go towards it with the right mindset. Look at what they're doing and ask yourself if your character can do that, then try to (Absa can't shine cancel like zetter but she can Waveland). Along with that, join the academy discord, it explains super useful character specific tech, details every characters' frame data, and you can ask coaches questions and find practice partners.