HELP! Game is too dark...

Have you tried adjusting your TV/monitor?

Or tried playing in a darkened room?

Have you tried a different resolution?

Yeah. Probably hardware.

try to change the hdr /dolby option

This.
Set the in-game High Dynamic Range to disabled.

Or turn it on, rather. HDR absolutely fixes this issue, if one is playing with HDR-capable equipment. I noticed that these very dark areas became incredibly realistic, in terms of lighting, once I started playing with UHD/HDR10.

Yeah, choosing the most optimal setting for your equipment is crucial. I hope it didn't sound like I was correcting you. I was trying to supplement, rather than replace, your comment.

I play on PS4 Pro with a very nice TV. I can't achieve high-end PC levels of performance, but this is a beautiful game in my estimation. Maybe I'm easily impressed.

Some of the coolest features are the small touches. The orange glitter on the "remnant" trees is realistically scattered on nearby items and structures. The bioluminescent lifeforms in Hvarl's water really look great. While in space, the stars and planets have beautiful, realistic atmospheric effects. The lighting is crisp and lifelike. Dust, debris, pollen and bugs are always in the air. It made me appreciate the artistic efforts of the developers. I'm guessing that many who trash the game's visuals never actually play enough to appreciate these touches; never got to see them; or simply don't care. The game has issues, no doubt; but there's so much that is good, also.