Who decides which are essential?
Is it the supermarket shelf stockers, produce delivery drivers, and admin staff that run the re-supply operation? What about utility suppliers? Gas, electricity generation and distribution and water/sewage don't look after themselves. Do we tell the police, fire services and other emergency services to stay at home?
That is the reason for lockdown. Essential workers represent a significant minority. you have listed only a small number - add healthcare workers for example. Unless everyone else stops going out to work or socialise we simply wont get the degree of social distancing necessary to beat the pandemic.
People have to eat and pay the rent, but most don't have the savings to live off their hump for a couple of months. Nor do their employers have the money to pay them without normal business inflow.
In the UK we are already there as is the rest of Europe. This isnt a case of 'what if' this is a case of 'what now'
The economic disruption will be profound, coming on top of the medical issues and before we have even considered the exit strategy.