I think saying he can't be a legend because he's neither our best defender nor has he won anything is to miss the point . You've got to consider context, including where we all thought he'd end up the season Nuno joined - as a squad player who covered CM and RB (at best). There's also his personality and attitude, things that can't be replicated (a manager's dream). He's also shown his adaptability, both in terms of converting to CB, but also the change in role under Lage.
Put to one side the fact he actually won the Championship as a mainstay in our team, to suggest not winning honours precludes a player from being a legend means we've had no legends since, when? 1988? 1980? Doesn't make sense to me.