I mean, yeah, but you know that's not the kind of life anyone's referring to.
It never hurts to be clear. "Lives" depends a lot on genre. I think what people are saying is they don't like lives in games where you complete stages and you are trying to gradually progress toward the end of a 15 hour+ game. There are probably other genres that lives don't make sense: RPGs and open world games, for example.
On the other hand there are still genres where "lives" make sense. Fighting games are a great example. Competitive games, in general, are often better with lives because a match only lasts so long. Roguelikes are another genre where "lives" make sense. From the beginning the concept of a roguelike is that you get 1 life and once you are dead, then that's it. Gradually roguelikes have let you carry a little bit over from one game to the next, but it's still basically built on the 1 life concept.
The original question was "Are lives an outdated mechanic". My answer is "no", because it depends on the genre and how the game is designed.