In an evacuation operation like that the first step is to get as many people out as possible, there is always somewhere refugees can stay for a short time before moving out to more permanent locations. Most likely, if the quick path between the neutral zone and Sol is some sort of high-speed fluke pathway they would be loaded onto transports of some sort and sent back to a safe location in Romulan space after they got as many out as possible.
And there has to be a lot of worlds in Romulan territory which are safe since the distance between the Romulus system and the Sol system is less than halfway along the long oblong of Romulan space (the capital is near one end and very near the Federation border). In fact, if the "supernova" was big enough to endanger much of the RSE territory it would have wiped out the Federation core worlds too according to the very map they use on the show.
We should also consider that its not just Romulus that would have been evacuated. Remus was inhabited as well, and odds are other worlds and even space stations were also in the blast zone.
All the more reason to get started early and not wait for the special evac ships to be built before doing anything at all. Kurtzman's bunch just don't make sensible plots at all.
The thing that maybe the writers for Picard realized but a lot of people don't is that it's not enough to move people from A to B. You need to have a B where these people actually can get food, water, shelter and medical care. And that's why you build a fleet of ships that will provide that after you reached B. The Galaxy Class will every only support that 15.000 people or whatever it's actual maximum is, and while it is doing it, it's not transporting anyone else anywhere.
Or recommission obsolete/old ships which would not necessarily be needed after making the trip(s). Which we actually did see them doing in 'Children of Mars'.
For that matter, TNG showed a huge mothball yard with hundreds or thousands of ships in reasonably good condition that could be readied in a very short period of time. And while they probably emptied out most of the better ones for the Dominion war the end of the war must have seen a lot of the kitbash and other rushed ships put in it (and the others storage yards like it) since there is no sign of them after the war.
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And there has to be a lot of worlds in Romulan territory which are safe since the distance between the Romulus system and the Sol system is less than halfway along the long oblong of Romulan space (the capital is near one end and very near the Federation border). In fact, if the "supernova" was big enough to endanger much of the RSE territory it would have wiped out the Federation core worlds too according to the very map they use on the show.
For that matter, TNG showed a huge mothball yard with hundreds or thousands of ships in reasonably good condition that could be readied in a very short period of time. And while they probably emptied out most of the better ones for the Dominion war the end of the war must have seen a lot of the kitbash and other rushed ships put in it (and the others storage yards like it) since there is no sign of them after the war.