Outdated may sometimes be a euphemism for one of the above but usually when I see it in a discussion it just means "old" or "out of fashion" instead.
However for pretty much any dev I would hire for a job they can get to grips with a technology that's older pretty quickly. Where it does get dicey is when good dev just refuses to work with it. For those devs, I think, when they hold that opinion it typically means one of those other reasons is behind their refusal.