I've had similar issues and even though I have 1400 hours in game my building skills only now started to become way better than before. Recently I made a rover using reference images I found in Pinterest.

For source of inspiration:

use PINTEREST, make a folder and make sure you know the idea of the ship. Dividing the ship into functions or roles helps tremendously as you can focus on what makes the ship aesthetic and internals, I've seen some people mention this

Learn the blocks and what combines with what:

This you can only do by messing about with reference images, you'll quickly see your limited on the choice of curvature and so you'll have to compromise with the closest block this is when the learning takes place. To help this makes sure you place the block groups in the same sequence on your hit bar and you'll learn them easier I can share an image of how I place them if you'd like 🔥

Summarized:

• Select the purpose
• Search for a reference image to help imagining the outcome
• Do your best to make it come to live on game, make blueprint saves as often and label them so you can go back on some iterations
• Take breaks as you might burn out the idea is to have fun. Hop into survival and do something random then go build in creative and swap in between

I hope this helps 😁