If this really is a “showcase” as you’ve said, I don’t think it’s very attractive. The grass is overly funky and neon and the same goes for the water. Everything is an obnoxious neon colour that reminds me more of Nickelodeon slime than actual terrain. I’m not even sure if terrain is what you’re going for; nowhere on Earth, or probably any fantastical representation of Earth, has islands that are mile-high, monochromatic cubes.
And on the topic of colour, there are only four colours in your whole game: bright green, bright blue, grey, and brown. That’s not a very good idea, especially when a player is forced to look at these bright colours perpetually.
So you’ve asked what you can add to it. My answer: nothing.
What you can or should do is to lower the amount of bright, obnoxious colours, reduce the temerity of the “terrain,” and bring some life and passion into it. Even so, you said yourself you did this a year ago and you stopped for several reasons. In which case, why not just start over from scratch? The entire place looks ubiquitously boring and would be better off redesigned and rebuilt. To do this, Roblox has a multiplicity of new (at least for me lol), modern features such as RGB for bricks, mesh terrain, smooth terrain, decals and textures… there are infinite ways to bring substance to your build and they can really help in giving a game a touch of vitality.
Good luck in whatever you aspire to do with it.