I think is crazy how much you have already done in this few first stages of development. The art and the gameplay have really good synergy to support the theme. It really gives "what if WALL-E would have been made for restoring the Earth's ecosystem?". However, I'm concerned with this Davin person who is doing all of the lore and dialogue.
Your decision to keep it as one biome and have a just a few NPCs and plants it's the right call. Content and feature creep will make the project fail. If you keep it as short as I'm seeing you are doing, this will be a great game.
The only concern I have is your audience. I might have missed it, but I don't think it appears nowhere in your GDD or your video. So far, I think it might not be a very accessible experience for younger audiences for the walls of text I'm envisioning in your lore, but I might stand corrected the next devlog you post.
I'm really curious about your gameplay loop. Best of luck!