No, going back to a 1950s style farming wouldn't solve anything.
We've got to maintain high outputs from reduced inputs.
Land availability for food production is coming under increasing pressure from other interests, such as solar, housing, road infrastructures, warehousing, etc.
Not least of these other pressures is land taken out of production for rewilding, tree planting and conservation projects. Worthy projects such as the work carried out by
@jall55 generally don't produce much food. His land could probably more profitably and productively be commercially farmed.
But that's not what you want to see.
And although our human population in the UK is high, which puts pressure on resources, immigration is not a significant factor with regards to food availability in the UK, despite what you might choose to believe. Net migration is falling.
In a nutshell, we need to farm more efficiently and more productively on certain areas of land that are suited to it, thus freeing up other land for other purposes, including conservation. And the type of efficient farming that's carried out has to be environmentally sustainable. And that is the direction in which agriculture is heading in the UK.