We call this abjectly missing the point

It all does rather depend upon the definition of necessary - possibly even who is doing the defining:

Green belt land may have been torn up for housing unnecessarily, campaigners believe, after the 2021 census suggested population growth in many areas has been overestimated – in some cases by tens of thousands of people.

But the census also revealed other estimates were far too low – by up to 16% – meaning local politicians now face pressure to allocate more land for homes than previously anticipated.

The mistake here is to believe that those politicians and planners should be allocating the land. For the aim of the British housing system - however we define or manage that - should be to build houses that Britons wish to live in, where Britons wish to live.

The entire point of the green belt system is to prevent this. Therefore it’s the green belt system that must go.

We can get into the grubby details here. For example, note the complaint by these folk that the information used is hopeless at the prediction of demand that the planners then use - meaning the planning system fails. Or we could note that we have the smallest new builds in Europe. Or that house prices are ridiculous as a result of the price of not land, nor houses, but the chitty that allows permission to build.

But the real and true underlying point is that the current planning system actively - was set up to do so - prevents the building of houses that Britons wish to live in where Britons wish to live. Therefore we must tear down that planning system.

Blow up the Town and Country Planning Act 1947 and successors. Properly blow up, bang. Kablooie!

Only from the rubble of that can we construct a system actually fit for purpose. Assuming that the purpose is actually to house us all as we wish to be housed, rather than as the elite would insist we must put up with.