The Church is defined by the First Council of Nicea as One, Holy, Catholic, and Apostolic.
The Orthodox churches are not united into One - they each go their own very similar-looking ways, but membership in one of them does not automatically cause you to have membership in all of them - not like how joining one of the 23 Rites of the Catholic Church gives you full membership privileges in the other 22.
They also, as you have already noticed, don’t have the same sense of urgency about making sure there are parishes within reasonable traveling distance of any and all potential members - so, they aren’t “catholic” (world-wide) in the same way that the Catholic Church is.
By contrast, did you know that the surface of the moon is actually part of the territory of the Diocese of Orlando? Pope Paul VI extended the territory to the surface of the moon when Neil Armstrong set foot there. So, if or when we colonize the Moon, the Catholic residents there already have a Bishop, and he will already be authorized to send them priests and build them churches, once the need arises and the technology becomes available.
In territories that are hostile to the Catholic faith, even in the cases where there are no resident priests or Bishops (or where the resident priests and Bishops have to hide the fact of their existence from the local authorities) the parishes and Dioceses are still marked out, and there are Bishops and priests who are assigned to be in those places, as soon as the situation becomes more favourable - it won’t be a matter of having to put out a call and hope someone responds - there are already priests and Bishops who are all set to step in, build churches, and gather congregations together, the very moment it becomes legal for them to do so.