At least in the UK I think you can at a high level map out some system level reasons why this sort of "public realm" problem doesn't get solved:

* the UK's economic growth has been poor since the 2008 financial crisis, so government resources from taxation have similarly not been growing as much as they used to

* demographics (more elderly people) mean that spending on pensions and healthcare has been steadily growing

* so the spending on every other aspect of government and other public-realm type things has been steadily squeezed: there are no resources for improvements on either the big scale or the small

* plus we have (like the US) a setup where many people and organizations have an effective veto or delaying ability on building things (houses, public infrastructure, etc), which makes fixing public infrastructure problems very expensive and time consuming.

As a water-related example of the last point: there's a proposal for a new reservoir near me which is classified as a "nationally significant infrastructure project". The timeline outlined at https://fensreservoir.co.uk/proposals/process/ started in 2022 with "pre-application consultation" in multiple phases, doesn't even submit the formal planning application until 2027, hopes to get a government decision in 2028, will not start construction until 2030 and might finally get the reservoir up and running by 2036 if nothing is delayed. And this doesn't account for the possibility of legal challenges to it which could add extra delay even if they are dismissed.