I must say you lot have a widely different idea of "oppressive" from that of mine if the Culture counts as oppressive by your standards. But to itch his own, as they say.
Anyhow, can't recall the teenager bit in Excession (doesn't quarantee a lot tho I only just finished it), but it is stated that the Culture is indeed consciously staying Involved instead of moving on to all-out Sublimation. IIRC it's also said that they aren't quite absolutely certain if they are doing the right thing, but they think what they are doing is still better than leaving things be.
I can imagine an advanced and essentially benevolent alien civilization might very take take that same stance with us, at that.
The dog, the dog, he's at it again!