The dark forest is a scary idea for sure.

The saving grace though is that it doesn't actually make any sense and can't really be true. The pure game theory of it all doesn't really work out. And on top of that, launching an attack on another star system is just an economically fraught endeavor. Given the technology required to accomplish it, it would be far simpler to build an immense Civilization in whatever star system you're in, there's no reason for conquest it's just too expensive.

Honestly, simulation theories are probably scarier because they're harder to disprove, in fact they tend to get stronger the more data we gather. And they're scary because should they be accurate, someone could decide to pull the plug on the simulation at any time....

Quantum immortality