LOL, I think this can be salvaged!
I am thinking the first thing to tackle is the retaining wall. Its okay its an angle, play it up :-)
I would get some stone veneers and apply them over this wall. You can go for a rustic look with boulders or something more modern with a cut stone. The world is your oyster there with all the variety they have. They are fairly simple, but time consuming to install but they will set off what your going to look at every day your enjoying the deck.
I would then put in a strip of garden at the top of wall, with shrubs, hostas, maybe some hydrangea's (for color) and also some plants that will cascade down the wall :-) All pretty self-sustaining plants :-)
The area between the deck and wall, this one is easy! Remove that baby and fill it with more shrubs, and some grasses. I would put in some tall specimens (of grasses) so that they loom up and can be seen over the deck. These will give you a look of a lot of depth and filling it up will eliminate the 'crevasse' look. Put down lots and lots of mulch and pack the area with plants so it doesn't look barren and get full of weeds.
As for the deck, I honestly like all the different decks because they create different areas. Dining, lounging, a walk-way (which is cool!) so I'd play that up. Get 1 paint color though and do the entire thing to not make it feel like add-ons :-)

I'd put in lots of planters with hostas and grasses (tie it in with the other gardens I just mentioned) and viola! Enjoy

Oh yeah, the tall plants/ grasses/ shrubs will hide the necessary 'uglies" around the house too :-)

Make the retaining wall more of a feature: add planters in front, paint or reface the cement blocks, and definitely plant low maintenance shrubs, grasses, flowers on the slope. Here are some pics for inspiration.

thanks great ideas! keep them coming- I'm planning of adding some garden in front of and maybe on top of the wall where possible...with a lawn area on the left side of the elevated section. I'm also thinking of removing the deck on the left & replacing with a patio to maximize the available space & open it up a bit. Im also considering extending the remaining deck off the kitchen in the center, so it comes flush to the wall instead of leaving the narrow angled strip between the deck and retainer...you cant see it in the photo but immediately behind the retainer there is a giant septic mound - so i've got to find a way to soften/camoflauge that a bit...and i'm thinking i should be able to plant some tall trees/bushes in a bed between the patio & retainer.

next up i'll share the disaster in the front of the house LOL

I'd keep the decks just the way they are...their shape is very interesting. The lower area in front of the retaining walls I'd put weed cloth and gravel. I wouldn't bother about fussing or planting in that lower area...just keep it clean and neat and weed free.