That's... kinda the point. It's why many (including me) think the most likely scenario is that we are the only technological civilization in our galaxy. There

That's... kinda the point. It's why many (including me) think the most likely scenario is that we are the only technological civilization in our galaxy. There are lots of natural objections to this statement (eg civilizations that "hide") and a lot of these has gone into these explanations for the Fermi Paradox. It can be shown that such a structure has massive benefits, the biggest of which is energy (which is our ultimate limiting factor). If there's 1 other civilization in our galaxy then we can't really guess what they'll do. If there are 1000 civilizatiions then what are the chances that none of them go this route, given if there's even one there's a reasonable chance we could detect it? It starts to stretch credulity.