So non-faith families get the places faith families don't want, and only those places.
Those places are in the schools were the faith families now don't need to apply to (a non-faith school), and that non-faith families probably wanted to apply to as it was their local school for example.
Just because a Catholic family want to apply to the new Catholic school rather than the other non-religious school, doesn't mean that those places are no good places.
If everyone had local schools with a mix of religious and non-religious options then there wouldn't be such a problem, as the case of families that are not religious and live in an area where all schools are Catholic.
The problem is things are more complex than that. It's not only that the schools are faith schools, but what their reputation and Ofsted status is. Otherwise, why are some religious schools so popular that people start attending church and pretending to be religious when otherwise they wouldn't do that. Or in other cases, when the faith schools are actually bad schools, and religious families avoid them and prefer to apply to a non-religious school that would suit the child better from the academic point of view.
There should be more schools to meet the demand and population boom, and all the schools should be good independently from the fact that they are or not religious.