I probably won't get in the alpha, but from the videos? Totally on par and even above the detail level in From the Depths. I spent roughly 100 hours in that game before I had a "boat" that was useable in any way. I imagine the learning curve will be the same here.
Obviously depends on the size of the ship, and how familiar you are with the editor.
My 1st ship, which I don't even use, it was pretty much just to learn how to use the builder, took ~10 hours.
My 2nd and 3rd ships took ~8 hours.
I'd say it's a bit more complicated than space engineers, you have to take into account cabling and pipes, structural integrity, and the fact that you can only use set sizes and shapes of parts. Starbase ships can get a lot more detailed than SE ships, but obviously that means longer to build.
That being said, SE can handle much larger ships due to using blocks instead of voxels.
Took me around 4 hours to figure out how to get my thrusters working and after that it was pretty easy.
Now building my ship took somewhere around 8 hours
Right now i'm just modifying my first ship till its impractical and I have to start over.
I think that most of the time I spend in the editor is not actual picking and placing of parts, but, like any design project, scratching my head. I spend probably 50%+ of the time "building" trying to figure out how I want to go about plating this, cabling that, etc.
I have only really made 1 ship, and variants of it. I tried making other ships but saw no motivation to continue after placing a few beams.
The ship I was working on in Closed Alpha, I tested rigorously, saw new faults and new ways to improve it with every test flight. I was trying to make a good fighter for kingdom, and wanted it to be good, so I spent a lot of time improving and reworking the design over and over again. Also used the ship as a testbed for other stuff. Overall, about 100 hours, including time I spent gathering just enough money to combat test my ship. Though, it was never complete.
For a rough estimate of how long it took me to figure out how things work, a few hours.