Problem with LTNs is that it is ultimately quite binary in terms of reaction, I don’t think they are an unmitigated disaster but they cannot work without behavioural change. I’m not sure I’d even have a car if I lived in London. It’s not the cyclists who damage & remove the planters & barriers at LTNs It’s a very difficult issue though.I lived there (again) for just under 2 years 2016-2018 and believe you me it happens and rather a lot... however, as I said, a lot of it is a reaction against the piss poor driving standards exhibited by so many and the crap infrastructure provided for cycling (even if, ironically, it is better than most of the rest of the country).
Interesting you mention LTNs... they have been an unmitigated disaster for people living on the roads all the traffic has now been forced onto... I'd have far more support for a council that just banned motorised vehicles completely provided they enabled proper and genuinely useful cost effective alternatives for people and yes, it would require some new thinking, but isn't that what we are supposed to do... make progress, innovate etc.
We tend to drive first & think later, making an awful lot of unnecessary short journeys. Used to do it myself, try not to now.