You get it wrong.
Nostalrius had a PvP server which was close to open AQ20.
They also had a PvE server which had just released DM.
So there are 2 servers, the older one with almost AQ, and the newer PvE one with still MC+Onyxia only.
PvP Server had a peak of 15k
PvE Server had a nice little peak of 3.5k-4k and it was a really good experience on there.
Lets just assume Nostalrius opens again, with both servers they had before.
There is your point (that is right at some point), that you can't compete. The PvP server is progressed too far. New players are (progression wise only) disadvantaged.
The PvE server however still would allow you to catch up and to do MC+Ony+ the probably soon released BWL.
Also, lets say they reopen and a lot of new players start, because they only heard about Nostalrius after the shut down, after the whole media attention.
There is a chance that they'd even open a third, a new, server to balance out the population. Nostalrius too wouldn't want a cap of 18k-20k on the PvP server and a similar high cap on the PvE server.
If thats still not enough for you, then you should just look for a new server/project. Or start on Elysium, they're not that far progressed yet either.