So I restarted the game several times, partly because I wanted to test something, partly because I got bored and partly because I screwed it up myself.

But for me the portals have never been a reason for this, they make some things easier, that's true, but they are not a savior.
Portals can be destroyed, do not let ores and metals through, nor are they prevented from sailing, they only reduce the time at sea.

My advice to you would be to try without portals, but possibly to have a portal in your base and the raw materials for 1 portal in your ship to be able to rescue you if necessary.