>>46510435>It's not that it's getting worse.Defensive sets can't compete with Lando due to the lower BST, and offensive sets can't compete with Salamence or the UBs due to lower attack and speed.
Gyarados has a great typing, two great abilities, and great coverage, but it's let down by its BST and primary STAB moves, which is why it's not good anymore.
Give it a 120 BP Water/Flying move, or give it a BST boost, and it'll return to consistent OU usage.