Theres a bug with fishing in MCMMO where if you hold your rod in your offhand then anything like a sword in your main hand, fishing is quicker and better. You can read more at this github post (mcMMO-Dev/mcMMO4921 ). You cant autofish using it though because it automatically swaps the rod to your main hand.
The suggestion is to add a setting which lets you toggle the ability to automatically swap the rod to your main hand or you can just make autofishing work with the rod in the offhand as well. If anyone knows any mod or workaround that I can use that will keep the rod in the offhand while having a sword or something in the main hand then please lmk.