Isn't that the point of the dark forest theory? It's not the fact that there is a dangerous tribe behind a bush it's more that you don't know if they're dangerous or not so you have to err on the side of caution - because you don't know if they're doing the same.

It's the whole chain of suspicion theory that it's safer to shoot first and then ask questions later because the speed you can communicate is the same speed you can mount an attack.

Time does not matter. Space-faring civilizations can adapt their pace of life to the communication and exploration speeds or even live at multiple speeds. They are likely energy and resource-bound: within the same theory Dyson sphere is a risk, so they can only consume a fraction of locally available energy to remain unnoticed - meaning that it’s not the distance but energy consumption that will limit them.

Of course, the risk is, thinking that centuries is a long time may be merely a human, and not a universal, trait.

Deploying decoy target requires more advanced technology (space travel) than hiding the signature (we may be able to do it long before we reach another star). I don’t think this is a good argument. Let’s say, some civilization decides to invest in decoy. It needs to shine brightly, the energy footprint is huge, a lot of work has to be done to transform the entire system. Then what? If there’s a hostile player, capable of destruction, they research and destroy the target, and start surveying the neighborhood. You cannot just build a decoy on another end of the galaxy, right? The further you have it, the more complicated is the task. And then you can only hope that the time left will be enough to collect enough energy (even if you have the tech) for defense.

It’s game theory, mathematics. Let’s say every player has 3 actions: do nothing, expose yourself and destroy the player you aware about. Your goal is survival. If you expose yourself in this game and there’s at least one player choosing „destroy“ action, you loose.

Now, of course there’s a question of applicability of this model: 1. are there other players? (if the game started, we won’t know until we observe destruction event - but that’s falsifiability) 2. do they have means to destroy you? (we may find out) 3. do they have motivation to destroy you? (we may find out) 4. can you protect yourself against unknown level of technology? (we may find out).

This theory meets scientific criteria, it’s just that those criteria require level of technology that we may not reach in thousands of years.