Hello and welcome back to the game!
Astral is as explained above, endgame content. your lv66 is levelling content for now. once you reach lv75+ you will get into the final questing story, once you complete that story line you will receive astral keys ( you can check when you press k, go to replenishables).
Going astral is as boring as queueing up now or making a party an instantly teleporting yourself to the allod. (this can be done on ctrl+M > dungeons)
Astral ships are used for non astral isles now such as demon hunting, anomalous sector (astral pvp) and enjoying content of what once was awesome, now is dead
As I may advice tho if you are a returning player or a new player, the best Allods there is for you is the subscription server because of how far behind you are on f2p CASH SHOP aspect. Sure they do gear resets every patch so players can "catch up" or atleast get that feeling. But no one dares to speak about the CS levels that are as high as hell now and how far everyone really is. Even with the new character "free CS you get", you are still regarded as a noob that won't do good in any endgame content because you're either useless, 2 shot, or underperforming.
My basic advice is to start a new adventure on the subscription server (league) where no CS is involved and where everyone is equal for the same pay.
if you really want to catch up on f2p because "but i already invested so much in my char" then you should be prepared to spend another 1500 - 2000 euros only to catch up - not being the top - with the players on this "FREE" server.
I hope I could help out on your decision and please ask more questions if you have.