Like you I'm an expert skier. The most difficult thing about learning to snowboard is that I see the awesome ski trail in front of me, and if I try to go, I'll just painfully fall.
I learned to snowboard in my 20s as an expert skier, and the only reason that I did it was that I had moved to California and so was skiing with a bunch of beginners, so being a beginner with them was a lot more enjoyable. Once they got good enough to ski blacks, I put away my board and haven't taken it out since.
I basically had the opposite experience last time I tried skiing. After snowboarding at least weekly for most of my teens, just going down the slope facing it triggers my reflexes and I keep trying to lift my toes.
It stinks to go back to being a beginner.