I mean, I know how to separate my performance with a character from my opinion of them. In the case of Corrin, I actually do better with him than with most characters. I'd attribute that to the ease of use of the character mostly, but still.
For what it's worth, I think the character is quite relevant and pretty strong. Character has good matchups against Mario and Rosalina, seems good enough against Sheik too. Beats Villager and Ness. Only really loses to Diddy and Fox, and arguably Mewtwo and a couple others. Solid, solid, solid. My qualms are to the character's future; I don't see much room to grow.