Yeah, that example is pretty crazy, I don't understand half of it. But the light streaks are easy to make:
https://www.dropbox.com/scl/fi/jwuqelur50c527xo7u6gv/ShinyCard.c3p?rlkey=jqm2zhqd4izqlyecpdypwgojq&st=jbg9skfe&dl=0
My issue with the way that you did this is that it's still tinted darker plus it's not fit to the shape of the card (for context, the opacity on the original is 100% and cards generally have rounded edges)
To fix the darker thing I set the blend mode to additive (which again isn't done in the original but whatever) But I still don't know how to round the corners of it.