I'm not all old-school, all the time. Actually, most of the game books on my shelf are "modern," and most of the games I've run in the past decade have been more in the modern style. To me, there are some games that should be played old school and some that really wouldn't benefit from it. Vampire, or most White Wolf games, would be a little problematic to do as old school games methinks. In fact, I tend to want to run fantasy and sci-fi games in the old school fashion, but not games set in the modern day or some other milieu. (Yeah, "milieu", a word I know only because of AD&D.)
I don't think you have to be all one way or all the other. Some of my players dislike the old-school, as I learned in the Warhammer Fantasy Roleplay "sandbox" campaign I ran for most of 2008. After all, you can like different types of video games or different genres of literature, right? Lately I have definitely been pining for some old school gaming action. I believe I might have to go outside my current group (*gasp*) if I really want to do that.
Now...above I mentioned that I don't run modern games old school. Now that I think about it, that isn't entirely true... ten years ago, I ran an In Nomine game very much in the sandbox fashion. I had a setting, with NPCs and what they were up to, and I dropped the players in with their own motivations. The really awesome thing is that some of the characters were divine and some were infernal, which meant that they were going to be opposing each other directly. (In fact, neither of the two factions enjoyed much internal harmony, for that matter) It was the biggest campaing I've ever run (nine or ten players by the end, if I recall.) It's still remembered fondly by those I'm still in contact with who played it, even though it ended in a fiery conflagration wherein the servants of the divine wiped out the servants of the infernal....yup, one half the group straight up killed the other half.
While that game was a smashing success, many of the other old school sandbox style campaigns I've run in the years since have sputtered and died due to lack of character motivation, except those games that were run with Cyclopedic D&D (and even that had a fairly short run.) I find that a lot of my players, when given the opportunity to do anything, find themselves not doing anything out of indecision. I suspect it might be because many of my players aren't used to sandbox gaming; they are used to tightly plotted campaigns and modules. Perhaps this is something I should have addressed more thoroughly at the beginning of the campaign. A lesson is here noted.