Consider my viewpoint as one in opposition to your own.
My personal experience—I've met people who are well read but don't read well, if you know what I mean. People who read Nietzcshe and think that they can get by with less sleep because they're übermensch. Yes, I've actually met two people who have come to that particular conclusion. I imagine that they eventually grew out of it, but was it reading, specifically that caused this, or just the general experience of life (of which reading is one part)?
If your attitude is that you are reading to challenge yourself with views that you disagree with, then you are going to find it easier to expand your mind. But that's not why everyone reads, not everything you read will expand your mind, and that kind of attitude will allow you to expand your mind in many other ways as well (besides reading).
I'm also not sold on the idea that youth are idealists in some kind of ideological sense. I feel that it comes across that way, but only because as I get older, I am a better judge of how I can actually change the world, and I might as well devote my resources to where I can make the biggest difference. In other words, we may become more or less idealist as we get older, but being pragmatic is literally a skill that requires experience to develop.
And if you doubt that you are still idealistic, remember that you are the one arguing that it's hard to "learn garbage" from reading—perhaps an ideological standpoint, from my perspective ;-)