As you highlighted, I didn't say that save features weren't relevant, I said that the trouble of including a save feature was no longer relevant. With modern hardware including onboard memory to store save files, it's no trouble at all to save whatever you want to save. Back in the 80s, though, it was a lot more of a hassle for developers to include save features, which was my point.
And having "unlimited lives", multiple checkpoints, and "save whenever" features makes dying inconsequential. I want to be challenged while playing a game. Ratchet & Clank has unlimited lives as well, and that makes the games boring since there isn't any punishment for dying.
Having unlimited lives doesn't have to make a game easier. I mentioned Super Meat Boy in the post you quoted, and that game gets insanely hard. It doesn't make the game easier if developers don't want it to, but it does remove pointless frustration.