I would rather live next to the south circular, than next to the north circular.
And maybe the north circular is less prone to congestion (I don't really know because I don't ever use it) but I'm sure it feeds congestion to lots of other roads, that would see less traffic if the N circular didn't exist in its current form. You have to look at the system as a whole... the worst congestion occurs at the pinch points. If you remove a pinch point, you increase the general capacity of the whole system and the pinch point moves somewhere else. If you carry on doing this, it's inevitable that all roads continue to get wider and wider and busier and busier. And then you end up with something like LA, where despite having multi-lane highways everywhere, they still suffer congestion.
Or Glasgow.
Much of what you've put is subjective.
I suspect those living in the area of the South Circ would probably disagree with you. And you're forgetting the wider knock on of 'do nothing' - the south circ isn't fit for HGVs in part, you may think that's not a problem, but how do you propose to replenish the supermarkets, DIY sheds, hospitals even with supplies ? The delays on the road network in the south has massive knock on effects on bus journey times, emergency vehicle response times as well as general private journeys.
Using Google Maps to demonstrate the point - to get from Hanger Lane to Tottenham is 12 miles and takes about 40 mins given current traffic.
Mortlake to Catford - same distance, takes over an hour on the South Circular. So a 50% longer journey duration, more time stuck in stop-start traffic, all increasing pollution.
You may not like roads, you may not want roads, but you can't disinvent them and you can't stop people using them. What should be done are things to mitigate the worst effects. Whereas with the South Circ, the GLC did nothing and it's a disaster area now.