I have seen no data in the past to indicate that Magic Luck influences fishing in any way.
This could be changed at any time ofc

Checked for the following:
HP/MP per fish (~ Same average)
Fish tier (~ Same distribution)
Rare fish frequency (Random AF)
Overspawn fish (Never seen one)

From personal experience I think not. I've caught many thousands of fish in and out of ML gear and haven't been able to tell a difference whatsoever.