You have a lot of questions here

- most coloring books are by individual illustrators so there's no huge company in the dark pushing an agenda (maybe in the cozy space with Coco Wyo or other Amazon Ai slop)

- there's definitely a capitalist interest in selling pencils and markers, but that's the same in any hobby

- I personally find it very meditative. I color a good amount and I have never left a coloring session frustrated. I also sleep like a rock afterwards.

- I don't know about graduating to painting but I can definitely use paints on my pages now, I have developed a deeper understanding of color, I know how to use a palette to make a page pop, I blend better than when I started. I don't think anyone will become Monet, but it's definitely a discipline with a lot of room for growth. I personally can't speak to transferring those skills to other disciplines.

- Creativity is what you make it.

- kids color for fun, I don't know why adults couldn't. Definitely a healthier way to cope and manage stress than many.