I'm not going to address every point individually, but to give some feedback on the decisions that we've made regarding the skin.
We're aware that the new backgrounds haven't pleased everyone. The choice of using water images is to fit in with OSMC's branding. To ensure readability of text we have a halftone image on top of that - the black-to-blue gradient. The upcoming update to the skin adds the ability to choose your own image instead of the water image.
The blue color we use throughout the skin is similarly a part of the OSMC branding. We use a single color for a number of elements, and having a color - rather than the black that was used in the previous incarnation - is particularly useful for highlighting notifications that appear and making it clear where the currently selected item is. The upcoming update to the skin adds the ability to choose a different colour for these elements. We've also made some minor adjustments to some text colours to try to improve readability, and will continue to review this.
One regular complaint of the previous incarnation of the skin was that it wasn't always clear which item was selected when browsing media. We've taken a few steps to address this, one of which is to ensure we display the fanart in the background when available to give an extra visual cue as to what item is selected. I'm quite happy to add a toggle to disable fanart - if Sam will let me sneak it in before the next update hits
It's also worth saying that for many people the cover image is an important part of how they browse their media, aping in some respects the experience of browsing your dvd collection on its shelf. However we make a list view available in all views but the home screen widgets, which can be selected from the left-hand menu.
The update to the layout of the homescreen was the result of a lot of internal discussion. Moving the submenu's to the left was done to reduce clutter, improve navigation (left for submenu, right for widgets) and to provide more visual consistency (so now submenu's, context menu's, view options all appear here in the same fashion.) The choice of the spacing and size of the main menu items - as with all elements of the skin - is something we will continue to review based on all the feedback we recieve.
We do read all feedback and will continue to refine the skin going forward. However, its impossible to please everyone all of the time which is why there are so many different skins available for Kodi.