Creating complex designs can often be broken down to simple shapes. Rather than getting stuck in details, build easy to create elements. Reused parts and rearrange them. Variations are the spice of your illustration. Once you got the base shapes in place, rework and add to them to create new elements.
With just the rectangle tool, rounded edges, some deformations and bit of tweaking you can create highly detailed scenes fast.
For the illustration at the top of the post, I added (Recolor Adjustment) on various parts to add the blue/ purple tone to them. It’s a nice and flexible option for a quick change in the atmosphere of your image.