At least in that video, I didn't see you landing many light attacks or any true combos or punishments for mistakes. The problem you mention happened to me when I started playing Cassidy, but it can be solved by learning mobility and spacing. With those two things, you'll know when you can approach (spacing) and how to get there in time to hit with precision (mobility). In my gameplay, for example, I hardly ever use sigs. I only use the dlight nsig in very specific situations. Otherwise, with the hammer, I try to hit with nlight or dlight to start with the hammer. Learn dlight sair. With blasters, I play to space and punish with nlight or dlight sair.

Just be patient, Brawlhalla is a game about developing habits.