I would agree with you that it isn't exclusive to old games. I pretty much do this with any game I run, but it's a little odd to me how much modern players *expect* a plot to move them along.
However....
"I personally love that sort of all immersible, creative, interact-with-the-world game, but I don't think there's anything "old" about it."
I beg to differ. This kind of "sandbox" play was common between 1974 and 1977, and slowly got eroded by how the hobby changed. The fact that there are still people who like this kind of game doesn't take away from that, but merely adds to it.
I agree with you, however, when you say, "there are GMs out there trying to get people to play that sort of game, not cause they remember it from "way back when," but because it matches their concept of what roleplaying means."
So I think we're in agreement when you say that this style of play isn't exclusive to "old" games - but I think you may be mistaking "old" games for "old school" style of game-play - they aren't the same. You can take very recent games and run them in an old school way; World of Darkness
sans background works pretty well this way, but 3rd Edition D&D breaks down because of the tight interlocking of the game mechanics.
If I'm mistaking you in any way, please let me know. There's a lot of discussion about these issues in a number of places, including the
odd74 discussion board and
James Maliszewski's blog; as you can imagine not everybody agrees about everything, but there's clearly an emerging sense of a different style of gaming.