Also speaking of galleries, what happened to the pop up that allowed me to change gallery shape, width, text colour, position etc. Do I need to learn coding just to do something that was easy to do before?
If I recall correctly, those were also accessed using the same "add image" button, correct? If so, then yes, you now have to use source mode to change those same things. The pop-up editor which allowed you to change those things were all part of Fandom's custom gallery extension which they are working towards retiring in favor the the software's default gallery system.
It may not be the best idea from the perspective of new/novice editors. However, most experienced users edit in source mode most of the time anyways and using the built-in gallery feature saves Fandom money be reduce the work they have to do to maintain the platform.