The retaining walls are what I like the most. IMO you need to identify what it is you don't like. Is it the style and/or colour of the retaining walls? Is it that they are just too overwhelming for the space? Is it the proportion of hardscaping to greenery? Is it that you don't like the space but are not sure why and thought that because the retaining walls seem most conspicuous they must be the cause? I am not saying that because some of us like them you should also like them. Each to their own. I agree with the concerns that the retaining wall would have too much movement for rendering to work. You would need to remove the wall and replace it with something you like, as suggested above. But it's a big job so I think it's worth having a good think about what exactly you don't like about the space. I don't think the pavers go well with the walls. Perhaps replacing the pavers would work? (What colour is the house? I assume it is to the right of the picture?) Perhaps growing more cascading plants would soften the appearance of the walls? Perhaps growing something taller to hide the fence would make the space more pleasant? Give it some thought. If you decide it IS the walls you dislike you'll probably have to replace them.

A lot of the time they build a core filled concrete block wall then construct another stone wall against it. The concrete block wall takes the job of retaining while the stone is for looks only. It does depend on what purpose the wall is performing. For example a retaining wall higher than 600mm (usually) needs engineering by a structural engineer which is easier to achieve with core filled concrete block on footings rather than just solid stone. You never mentioned the purpose of the wall which is a vital detail as there can be numerous ways to achieve similar outcomes.

Love love love my QQ Dolce benchtop. Have now decided to go with a tiles splashback and am very happy with the result. BTW, I rejected the original QQ Polar benchtop because it was very white and the sample was a muddier white. QQ was very helpful in rectifying the issue for me.

the black marble with white stone veins through it. the picture you uploaded seems to have a name of milky way on it.