So because it's small and far it's not a planet?
Scientists just need to admit they have a hard time agreeing on a definition, or that there are edge cases where a distinction is difficult to make... and just because there are edge cases which blur the lines doesn't mean we abandon the category altogether (like we're tempted to do with gender).
I just read about the amount of light at Pluto, and it's around 60 Lux, which isn't too bad. The author said it's about the brightness of commercial stairwell lighting.
https://www.johndcook.com/blog/2018/...read-on-pluto/
Pretty interesting. I wonder how far away you'd have to be before you could no longer read a book using sunlight?