The whole design process is based on imagination, You can't design something without creating a blank canvas first.
The correct design process is first you have to know what you want to design, imagine it from scratch, then start the process.
If you are really interested in designing a great GUI then i would recommend that you learn photoshop, create a blank layer, then start the design.
Once you finish creating the design in photoshop, start applying/programming the design in B4X, this way you will be able to tell which colors to set, where to set the fields, how to resize them, etc...
B4X, Android Studio, Flutter , Xamarin ,etc... all of these tools give you the basic design tools like a Layout, Designer, Coding the controls on runtime, etc... and the rest is on you.
With that being said, there is no such thing as "developers with no sight at all", it's either you want to make an effort to create a really great GUI or not.