What determines if a player is unclickable/greyed out when they retire? And what determines whether they are clickable? I would've thought they'd be unclickable if they played limited games/not a real league/team effect, instead I'm having starters who played 11/12 seasons for me become un clickable to check history after they retire but some backup qb's who have never played a game remain clickable.

They stay clickable if they've set records, won awards, multiple championships, etc.