"This was during some sort of story-driven tutorial in which biters would swarm a base after a few minutes of play, so research wasn't relevant"I have heard of this issue, and have seen a screenshot of someone else in the demo where the game placed the biters way, way, way too close to the player's base. That's just unfair, especially for a newcomer to the game.
I'd consider this a bug in the demo, and would report it as such to the developers.
In my own playthrough of the demo, about a year or two ago, I did not have this issue. The biters were well away from my base, and I had ample time to research the technology I'd need to beat them by the time they became a serious threat. I think they must have messed up the demo sometime after that.
The workaround for this is to play the full game, and forget the demo. There are plenty of tutorial videos on youtube which you can watch which will help you with any part of the game you don't understand, and in the full game you can choose a map that doesn't have any biters near by (or even make them peaceful so you don't have to worry about them at all).