It's not a contest.
But it is. There are only a limited number of ideas we can work on, so we'd better have some reason to think that this idea has more potential than any of the innumerable other ideas we could be working on instead.
There are only a limited number of ideas we can work on
You are right in general. However, it is also a mistake to limit your scope to too few of the most promising ideas. Suppose we put a number K on the number of different explanations we should consider for the Fermi paradox. What number K do you think would give the best tradeoff between thoroughness and time?
The Fermi Paradox leads us to conclude that either A) intelligent life is extremely improbable, B) intelligent life very rarely grows to a higher-level civilization, or C) that higher-level civilizations are common, but are not easy to spot. But each of these explanations are hard to believe. It is hard to believe that intelligent life is rare, given that hominids evolved intelligence so quickly. It is hard to believe that intelligence is inherently self-destructive, since as soon as an intelligent species gains the ability to colonize distant planets, it becomes increasingly unlikely that the entire species could be wiped out; meanwhile, it appears that our own species is on the verge of attaining this potential. It is hard to believe C, since natural selection favors expansionism, so if even a tiny fraction of higher-level civilizations value expansion, then that civilization becomes extremely visible to observers due to its exponential rate of expansion. Not to mention that our own system should have already been colonized by now.
Here I present a new explanation on why higher-level civilizations might be common, and yet still undetected. The key assumption is the existence of a type of Matrioshka brain which I call a "Catastrophe Engine." I cannot even speculate on the exotic physics which might give rise to such a design. However, the defining characteristics of a Catastrophe Engine are as follows:
The Catastrophe Engine is by no means a conservative explanation of the Fermi Paradox, since only the very most speculative principles of physics could possibly explain how an object of such destructive power could be constructed. Nevertheless, it is one explanation of how higher civilizations might be hard to detect as a consequence of purely economical motivations.
Supposing this is a correct explanation of the Fermi paradox, does it result in a desirable outcome for the long-term future of the human race? Perhaps not, since it necessarily implies the existence of a destructive technology that could damage a distant civilization. Any civilization lying close enough to be affected by our civilization would be incentivized to neutralize us before we gain this technology. On the other hand, if we could gain the technology before being detected, then mutually assured destruction could give us a bargaining chip, say, to be granted virtual tenancy in one of their Matrioshka Brains.