I think Nero has a hard time as a new Protagonist because he is so similar to Dante.
If V had been the new main protagonist in DMC4 and they had been building upon his gameplay in 5 such a transition would be way easier.
But Nero is essentially Dante with less options and a gimmick (at least in 4 it felt that way for many).
It also didn't help that his design was also pretty similar to Dante's in 4, as well as some of his mannerisms.
I guess what I'm trying to say is, if you're going for a new protagonist, don't do a copy & past job, either make it a new character or leave it at the old cast.
If V had been the new main protagonist in DMC4 and they had been building upon his gameplay in 5 such a transition would be way easier.
But Nero is essentially Dante with less options and a gimmick (at least in 4 it felt that way for many).
It also didn't help that his design was also pretty similar to Dante's in 4, as well as some of his mannerisms.
I guess what I'm trying to say is, if you're going for a new protagonist, don't do a copy & past job, either make it a new character or leave it at the old cast.