I'm not sure it's the Radiant AI system itself responsible here.
It should be a better version of the engine compared to Oblivion, and in Oblivion that people did all these things wasn't a matter of the Radiant AI, they had AI packages telling them to do all this, several of them.
I rather suspect in Skyrim the devs, as usual, took the easy way and reduced the amount of individual AI packages per NPC by quite an amount. Going by past experience that's pretty much to be expected.
If the NPCs don't do these things now, it's not because the Radiant AI is 'downgraded', but simply because there are no AI packages telling them to do this in this game. They were simply left out.
As a matter of fact, the AI in Oblivion actually can be called 'more' robotic than what they say about how things are supposed to be in Skyrim.
In Oblivion 'everything' was scheduled after all. And the NPCs were working down their schedules just like machines. It just felt more lively and dynamic to you, because the schedules were 'massive'!
Whereas in Skyrim, if your observations are correct, they seem to be tiny in comparison and seriously feature-lacking. And there's only so much a clever 'dynamic' AI can do to undo the damage done by the lacking.