But as you said public works are slow. If we build it now, people benefit from the change while we figure out how to improve beyond our current thinking/physical situation. If we wait everyone has to deal with the current issues potentially forever since we should always wait because there will always be a better idea further down the line. Yes it'll never be a perfect solution but its still objectively better than the status quo.

Also yes there my be unforseen issues caused by our implementation but there will be unforseen benefits as well. Is the glass half full or half empty....

There is also semi-related known benefits like in the case of major public works and investment in infrastructure, they are usually pretty good for the economy.

I understand your point that there is no such thing as a magic bullet solution. However you saying that in response to proposing well done cycle infrastructure as a solution is a perfect example of "perfection is the enemy of good".