Dublin has had strong restrictions on building height since the 1960s. An argument for this was to maintain the character of the city, although the destruction of many Georgian buildings was allowed by planners, on spurious health and safety grounds.
The worst effects of the policy were felt during and after the boom of the early 2000s, when accommodation was built further and further out from the city, leading to sprawl, and a commuter belt that stretched 100 kilometres in all directions, which put immense pressure on transport infrastructure. With so much construction, this represents in hindsight a missed opportunity to create more liveable centres or hubs in the style of London or other large cities.
Allowing taller structures for residential purposes in central city areas, would have improved Dublin's liveability. Instead, there is now a critical housing crisis that no one seems to know how to solve.
I believe it captures most of what is important in making a livable city that people enjoy living in.
As for the narrow streets, I am not questioning their charm, but they make transportation very slow, and therefore make it difficult to build out to compensate not builing up.
Tokyo is another interesting type of urbanism. You have very large avenues delimiting blocks. The blocks can either be residential, in which case you walk in what feels like a quiet little village with its narrow streets. Or they can be "entertainment", with a dense web of noisy bars, restaurants and game arcades, lots of light and people.
Are there limits placed on the heights of buildings in residential areas of London?
As for narrow streets, I'm glad they kept them. Compared to some other big cities London feels more 'human friendly' (for want of a better term), wide streets can make a place feel more car focused, less a place that feels like a destination and more somewhere you travel through to get to where you want to be. Dedicated bike lanes are the only changes worth making IMO, but you can create that by working with the existing roads so long as you reduce the demand for cars. It seems that the London Underground has been increasing in capacity over the past 10 years or so, hopefully that will continue.