I would suspect that you may be having a specific problem with storytelling (which is not quite the same thing as writing.)
I myself do a lot of worldbuilding for fictional purposes, and your description:
"I will spend large amounts of planning the geography so small pockets of interesting species can live secluded, how the trade between countries work, what the impact of mushroom forests could have on wildlife, how airships can be used in warfare, and so on"
feels very familiar.
For what it's worth, I think that worldbuilding and storytelling are very different headspaces. They use different facets of the creative mind, and my suspicion is that not too many of us are good at doing both at the same time. (In college, when I was simultaneously majoring in Physics and Art, I ended up having to trade semesters off rather than do a blended curriculum. I experienced strong mutual interference: my art sucked and my math/physics were way harder when I was trying to do that.)
When you say
"After writing a chapter or two I get bored and abandon the project"
it makes me think that you have a hard time telling stories when you're still in your worldbuilding mind.
Don't know if it will work, but you might want to consider this:
Build your world.
Solemnly pinky swear to yourself that the world is no longer subject to edits, at least for the time being.
Tell stories set in that world. If necessary, pretend you're writing fanfic about someone else's world.
Don't bail out too soon. It's likely going to suck for a while until you get good enough at storytelling to make your stories about your built worlds good enough to fit your worldbuilding. (My experience: I'm still a marginal storyteller and a very good worldbuilder. I keep telling stories...)
If, after long earnest shrewd effort, you can't get your storytelling up to scratch, maybe you should find a collaborator who's a damn good storyteller but who doesn't do worldbuilding very well. :-) Hey - it could happen, and it might work out.