Fates also does have honestly the least interesting protagonist in a Fire Emblem too.
That's saying a TON considering that many FE protagonists hardly have any character, not all, but a lot. Mainly Lyn, Marth, and Roy. Leif and Alm from what I've heard. Some come close like Eliwood and Chrom, but not quite. Even Hector, as much as I love him, somewhat comes close even though he is a different and more interesting archetype, he's at least a more interesting one which is what leads him to be far more liked.
Corrin regardless of whether or not you like them is actually vital to the story and has actual conflict besides the simplicity of completing a quest of sorts. And I find Corrin to be more interesting than Robin anyway. Especially since Robin suffers from a badly handle plot(that had potential), which also what holds back Chrom as a character too. It's not that uncommon for main FE characters to be not that interesting overall, other units tend to easily be more interesting. I think Ike and the FE4 protagonists are the best in terms of character though. With Ike being my favorite overall by far, since he's not only great in character but especially in gameplay. I also like really the Sacred Stones protagonists, but Lyon being such a great villain and their relationship with him is a big reason why.