I've seen it happen even as a young person, and still saw the fallacy of this "argument". I've been arguing with people twice my age who used it to silence any criticism of trends.
And it's totally an online thing, too. It's usually used to dismiss a thing without looking at the thing. Because if you could dismiss the thing by looking at it, you wouldn't need that old chestnut.
I don't blame young people for having less to look forward to than previous generations. I don't blame them for being unable to code, and so on. Blaming them for their lot is totally orthogonal to even having a honest look at what that lot is.
I never thought of a new generation failing the one's before it, being "lost" -- rather the other way around. We failed them. And by the same token, I also never dismissed people as being old and knowing nothing even when I was 20. I simply never once rolled that way, and I see nothing interesting, much less truthful, coming from it.