I love the new FSS, OP's reasons for why exploration is broken is exactly why I think it is finally fixed.
1. Yes metal planets/amonia planets/ice planets look similar. What do you think gives them their looks? This isn't NMS for goodness sake.
2. FSS is finally involving to use, and isn't just a honk and jump.
3. Nebulae lighting up dark sides of planets as if they were bathed in sun light was just ridiculous.
I think the inside of Nebulas would be bright. All the starlight reflecting off the gas would make the nights brighter. Just like when it’s a low overcast over a city. The city lights reflecting off the clouds can light up the landscape