It’s not, particularly, without unjust laws like three strikes.
For one thing, it’s a revolving cast of a few dozen people at any one time (people do go to prison, get rehabilitated, move on or get moved on). For another, they are often vulnerable or exploited: a lot of shoplifting is done to order, to supply the black market.
The UK does need to take shoplifting more seriously, but it’s important to understand that it is a consequence of both the design of retail (self-checkout and fewer staff) and of the cost of living.
There is nothing unjust about being expelled from society when you are found to be too damaging.
What is unjust, though, is to be the victim of criminals who benefit from knowing exactly what the threshold is to not being removed from society.